Preface this by saying that the game is feature complete. What you have now is what you'll be getting full release. As of right now I am only working on bug fixes, video tutorials, translations, maybe a missing map or two, text content (mostly manuals and code commenting).

After release, I will attempt to crowd fund additional work to the game via a feature bounty system. However, feature bounties are subject to user financing and votes, so nothing is guaranteed.

Will new events be added to the game such as: diseases, earthquakes, hurricanes, terrorist attacks, changes of government, temporary confrontations on the borders of nearby States, formation of alliances, etc.

Base City Map and Base Territory maps already have thousands of events in them up to 2017. Anything beyond 2017 has a 50/50 chance of being added before release, but is not guaranteed.

Most events do not directly affect month long vehicle sales in any meaningful way. At least not worth the amount of time to model them.

Let's break down each event you're asking about:

diseases

There are only two major disease events that affect vehicle sales. The Spanish Flu is already simulated via post-war recession. (Not to mention the war itself). The other event is the recent COVID-19 mini-crash, which is not modeled in the game because recent events have not been added.

Most other pandemics had very little impact to vehicle sales beyond localized mini recessions. City level economic events are not modeled in the game, but any effects they had on a macro level is already modeled.

earthquakes, hurricanes, terrorist attacks,

These typically do not have any impact on vehicle sales over a month period at a manufacturer level. They do affect dealerships, but the vast majority of dealers in the world are franchises.

Major events of these types are in the newspaper, but they don't affect sales beyond any macro economic changes they cause.

changes of government, temporary confrontations on the borders of nearby States

Government changes for cities are already in the game for every map between 1900 and 2018. Base City and Base Territory maps include newspaper clippings for every war and minor conflict between the same years. Every war up to 2018 that impacts city factory or branch operations are implemented in Base City Map. Classic map should include up to 2012 or so.

So in the nut shell, all of this is already in the game. If you want to add more effects of events, use the Turn Events editor in the mod tools.

formation of alliances,

The game currently has no concept of country beyond a string for the name of the country. That's why it's called "GearCity". There is a feature bounty ticket to expand upon country level data and add relationships between countries, thus opening up military contracts during war time, for instance.

I would also like to see the ability to edit the number of valves in the engine, greater variability in the size of the piston and its stroke, the ability to choose the type of engine intake system (mechanical or electric).

There are feature bounty tickets to add more variables to the component designers. Unless they are funded, your only option is to use the mod tools and add more options to the sub-components system.

Whether it will be possible to design CARGO chassis and not just small-sized ones for urban transport, i.e. cargo tractors or even buses.

There are feature bounty tickets to add more vehicle types to the game, including large vehicles. There is also a feature bounty ticket to change the classification of a vehicle based on its size rather than by selecting a class.

Until such bounties are funded, your only option is to the use the mod tools to make such systems.

And I would also like to see an endless game mode in which there is no end date for the scenario, so that each time you do not restart the game, and where AI companies appear as the leading companies disappear, up to a certain number of companies.

Already exists in the game.

It is also frustrating to not be able to choose the type of material for the engine, chassis and body. Opportunities to put various accessories to improve the interior of cars, choose the type and size of brakes, multimedia and other features.

I'm personally not a fan of endless check box lists that overtime are all checked because they're standard features. So that is why much of this stuff is abstracted in the game. A CEO doesn't care if an engine block is made out of cast iron or aluminum. They care about specs and costs. The engineers are the ones who make the design decisions.

That being said, this is an often requested feature, so it is in the feature bounty system. If funded, and voted upon, it will be implemented.

And I also want to see the possibility of modifying factories for casting, working with new types of materials, automation, creating warehouses of components, which would also allow us to organize planned production in a short time of equipment in case of need (military contracts, or demand checks or limited series of cars) in order to be able to actually produce machine kits and send them to other factories.

Much of this stuff was abstracted because, again, CEOs don't deal with logistics. That's the job of the logistics engineer/manager.

That being said, there are feature bounty systems which will change the factory production system. It won't go into details about material types, casting, or automation, etc. But it will change the system to be more realistic, in that you have to plan in advanced the maximum number of units you want, and then it will take several months to tool the factory to do that. You won't be able to change models or increase production beyond the maximum amount on the fly as you can now.

Originally I intended for players to manage production of components and have inventories, but I found this to be too much micromanagement. That being said, it is a feature bounty system ticket pending of the above changes to the production systems which will add component manufacturing requirements for vehicle production.

And as it was already written above, it is possible to design heavy vehicles, for example, I would like to see the opportunity to design a special transport that has 4 or more axes.

I believe each vehicle class will come out to around $5,000 each. If you want Semis, Cargo Trucks, Buses, etc. We're more than happy to add them if you can come up with the money.

In the end, the game has the closest competitor Automation - the Car Company Tycoon Game, for this reason, the game all this is directly necessary, because this is not an arcade game and the more functionality there is in the game -

Sadly, GearCity is 11 years old now, well past its technological expatriation date. It's also hasn't been successful enough after Steam Direct for me to justify continued development on it, especially after COVID wrecked my other source of income.

Automation on the other hand has 10-30x the budget, thanks in no small part because they had an artist on their team from the start and they focused heavily on graphics over being a game. They had the resources to become a mod tool for a more popular game, thus snowballing their resources. So there is no competition between the two of us. They already won when they had the resources to switch off their own engine.

Most of what you ask for is already implemented or can be modded into the game using the modding system. Beyond that, unless the community funds additional work to the game, what you have now is pretty much the final product. I can't afford to continue working on the game for just above minimum wage. (Or actually, soon to be less than minimum wage. Since we raised it recently.)

Glad to know that developer say that he is stopped any actual support for this game using this punny reason is named "Budget", like developpers of project 5 sighseer and many others just to throw product and say "it is done, use it as is or not". And for all this reasons, even mod community can't fix that not implemented on game engine, just because it is competition for developer.
Very sad to know that, just because that game have huge potential, that was wanished by dev...