Jolly 4 takes place after Jolly 3 chapter 2

"Finish what he started"- probably reffers to Eric Liam`s attempts to hunt down William Afton, who was the reason of his death in classic Jolly suit, to avenge his family`s deaths, and also maybe to help souls possessing other animatronics to be able to rest. In Jolly 3 chapter 2 he goes down to the underground facility, because he knows Springtrap/William is here, but in the process he reunites with his family, and decides to leave everything behind and rest himself. In jolly 4, we play as protagonist from both Jolly 3 chapters, who now tries to release souls possesing the animatronics.

In Jolly 4, souls which possesed classic animatronics now possess Goodtime animatronics.

Goodtime Jolly is not possesed, but is a security animatronic.

Goodtime Tal is possesed by Tony Audrey`s agony

There will be regular 5 nights, and afternight tasks like in Jollybee`s

There is no regular camera system, but multiple screens hanging on the wall, which show different parts of facility.