Speculations:

*Five Nights at Candy's 4 May take place in:

-Headquarters of Rowboatics Corp. after being abandoned (or not)

-The same location from FNaC 2 but in a different area

*The creator of "Prototype Candy":

-Was murdered and his creations were sent to Rowboatics Corp. to hide what he created and test for future projects

-Used Rowboatics Corp. to hire people to test his creations, to make sure they are perfect, then may have died there

*The Protagonist:

-Works as a testing subject/mechanic of the building, or works in some sort of way in secret with Rowboatics Corp.

-Is an investigator (this could explain the "do not activate the animatronics", but it could just be "do not activate the animatronics by yourself", and then the "do not bring anything with you" wouldn't make too much sense if this is the case)