You also asked on my game how I moved the dumpster-- No real magic there, I just had a duplicate room with the dumpster one over.
Rooms changing with new dialogue and objects after you do some tasks -- Again, just a duplicated room, with the sprites and everything placed back in place.
LArger sprites for the animatronics -- No magic, just two sprites on top of eachother!
Spots where you see dialogue without interacting with something-- those are just invisible items on the ground with text attached. Tiles are what make up rooms, Sprites are interactive objects or tiles, and Items are things you pick up and can walk through. So I just did some items with no image so you walked in and text happens.
You can put conditional effects on dialogue using the BRANCHING list option for dialogue, so for the Wrench in facing Freddy, that's all I did. If you had the Wrench, the game went to one ending. If you didn't, it went to the default, bad ending. There was also a gun ending that was a bit happier than the wrench one! : )
How I darkened spots of room? I think you mean like the Attic-- that's again no secret magic, just different rooms. Exiting to another room over and over so it looks like youre in a moving vision scenario.
Dialogue choices.... I think there are some hacks that let you do that, but I've never used them personally. IT just adds a whole nother layer of complexity that I don't always want to deal with haha.