1. "Meet All the characters" achievement is unlocked in all the save files.
2. The first ending is unlocked in all the save files.
3. Description of achievements have been omitted. You can read them in other guides.
4. The save file for the game is located in C:\Users\*YOURPCNAME*\AppData\LocalLow\Nerial
If there are any issues then let me know and I’ll reply as soon as I can

When you load the save file you will already be in the dungeon with Excalibur equipped (it makes it easier to win a duel). The skeleton is already defeated 2 or 3 times. You can stay in the dungeon indefinitely and kill him as many times as you want. You can still get killed but if you do, just reload the save.
Download[drive.google.com]

In this save file you have already governed 99 years. You need to survive till 101 year to get the achievement. You would also get the "Elder" achievement if you already did not have it.
Download[drive.google.com]

This save file will get you to year 1998. Get the first ending, the achievement will unlock, load the save file again and rinse and repeat for the others. You would also get the "Millenium" achievement if you already did not unlock it.
Download[drive.google.com]

This save file is saved in the 1990's with 28/29 deaths unlocked. The strawberry quest is completed and all you need to do is use the death wish on the skeleton when it appears. It is the only death that has not been unlocked.
Download[drive.google.com]

There is some disagreement about when this achievement would unlock, some years ago -according to the developer- there were 770 cards and it would unlock at 750. Now I think there are around 870 cards and would unlock at 850. I read some posts about people unlocking it around 840 or 842 while some people did not get it even at 850. I got it at 843 cards.
Download[drive.google.com]