So I have played through the game to the end on PS4, but there was one scene that got me a bit confused.
When Batman decides to let Robin lock him in the last cell, we then see The Joker again as we know he is not really alive, but no mather he let Batman out of his Cell, so that he can Finish telling his Jason Todd Story. And then at the end The scene with Robin (Tim) starts again only this time we can resist and put Robin inside instead, So that Batman is free to take care of Scarecrow. The first time I just walked into my cell again, and The Joker let me out again untill I resisted and Put Robin inside.
But if The Joker is something inside Batman's head how the hell did he open up the door for Batman?
The idea with this cell was that Batman himself could not get out so Batman did not let him self out, so that whole part confused me a bit, it's not a big deal just something that don't quite make sence to me, or maybe I missed something? Perhaps Batman is stuck in the Cell the whole time and just imagine the rest of the story :)

Everything that happens after Batman initially walks into the cell happens in Batman's head before he is locked in. Then the eventual resistance from his part is what actually happens in the first place.

So he don't get locked in it's just him imagine in his head, and then at the end before he is going to get locked in for real that were he resists and choose to lock Robin in.

Ahh okay that makes sence, I just could not figure it out while I was playing, thx for clearing it up :)