The glitched levels will be unlocked once you complete a certain amount of minigames total. Simply continue completing minigames, and you will obtain the Faz Wrench If you are familiar with Security Breach: Ruin then you should know what to do. Otherwise, go to the orange station with wires on it in the corner of the room to the right of the Stage. Put the faz-wrench in the socket, and complete the puzzle. You should be able to figure out how to enter Hard Mode from there. If you're stupid like me, and can't, then place your hand up to your head and grab.

Similar to unlocking additional minigames, you just have to continue completing minigames. You will receive additional prizes via gift-boxes that appear on the stage. After you unlock these extra minigames, check the stage every so often and open the gift boxes every time you see them. Upon collecting the final prize, the ending will occur.

This final minigame isn't locked behind the other minigames like Pizza Party was in the original Help Wanted, but rather a secret route taken through the minigames.
The route begins in Fazerblast 1. During the game, you will notice a rocket move by. Shoot it, then complete the minigame.
Next, move on to the next stage of Fazerblast. During the part with the trains, keep shooting the targets on the train cars to keep the windows open. Eventually, you will see the rocket fly by in the background. Shoot it. You'll know you did it right if the rocket goes haywire and knocks over a hay-bale.
Next, move onto the next stage of Fazerblast. Near the end of the level, it will rise up from the center of the shooting gallery. Shoot it. You'll know if you did it right if the rocket goes haywire again and knocks over an oil barrel.
Finally, in the last stage of Fazerblast, you need to get a score of 7380 points or more. Heres a quick guide on how to maximize your score during this final, difficult section.
First of all, except for the opening with the children, and one case I'll cover in a moment, don't worry about throwing the balls unless you are really good at it. It's not worth the points.
Secondly, each animatronic has a different way you need to deal with them. These will all be familiar for those who have played FNAF 2 or it's HW variant before. Move around the cameras and keep the Music Box wound. If you see someone on the cameras, you will need to act quickly to deal with them. Succeeding will gain you an opportunity to gain extra points, whilst failing will result in a cardboard jumpscare, which will block the screen for several seconds and stop you from getting more points until the static disappears.
Here's how to deal with each animatronic after you see them on the cameras:
If you see Withered Bonnie or BB in the vents, check the left vent and blast them with your dart gun.
The same goes for if you see Toy Bonnie, Toy Chica, or Mangle in the right vent.
If you see Withered Foxy in Parts & Service, the camera will go down. Shoot the button on the top of the office and then throw balls at him to break his different pieces.
If you see Toy Freddy, the camera will go down. Shoot the button next to the Freddy Mask in the office.
If you got a high enough score, the entire level will burst into flames. Congratulations, you have unlocked the final minigame, and your first step into the secret ending.

The process of getting this secret ending starts after completing the final locked minigame, so unlock that first via the above section before you try to get this ending.

There are 6 collectibles you need to find scattered about the different minigames. I will first give a hint as to where they can be found, then I will give a spoilered, more direct guide.

Complete the final, hidden minigame. See the above section.
To complete Fazerblast - FNAF 3, you need to kill Springtrap. First, break his suit pieces using the balls. You need to hit his two legs, his arm, his head, his torso, and his waist. Then, shoot his balloon innards with your dart gun. Once you break the last balloon, a target will appear on his chest. Shoot it, and he will appear in front of you. Blast him with your lazer gun until he falls over, and receive your prize

Bonk-A-Bon, Bonus Round. When the machine breaks, dont fix it normally, but enter a code.
You need to enter the code it gives you, but backwards.

In Fazbear Theatre. Combine all of Chica's items.
You need to put all of them in the trash.
You need the Lemon Chica Bar, the Chica Chowda, the Chica Chug, and the Strawberry Chica Blendee.

Get the secrets in Captain Foxy's Log Ride. Ensure you hit all the Star-like symbols.
The star-like symbols are all found in Helpy secret routes, which you should remember from Curse of Dreadbear and it's version of the Log Ride.
The first Helpy is found in the area with the Brightstone sign. The first star is on top of the streamers in the hidden area.
The second Helpy is found in the turn right before the train section. React fast and hit him quickly. The second star is above one of the doors in the hidden area.
The final Helpy is in a minecart during the mine segment. Hit him quickly as well. The third star is leaning against a stone post on your right near the end.
The final star is on the birthday cake at the end of the level.

Make a special drink during a Lockdown in Fizzy Faz Night 3. The game calls it a Graveyard, but it's also known as a "Suicide Drink", "Swamp Water" etc.
You need to first enable Lockdown, then very quickly fill the drink with Sodaroni (theres a can next to the order machine) and then fill it up left to right with every ingredient.

The SL drawer is unlocked in one minigame. You know what to do.
In Office: Puppet Master, open the drawer and type "1983" into the keypad.

Once you have every collectible, a reward will be waiting at the Mystical Hippo stand. You can figure out the rest.