I have beaten 4th gym- Erika and my bellsprout (Hm cut learned) level up, I replaced a move on the cut, and then I can't move out.

I'm a little confused by what you mean? You tried to replace cut and it worked or didn't? Where can't you move out from?

 

Have you tried to go to your backpack and relearn cut?

 

Also, don't quote me on this. I read this somewhere and don't know if it is true I've yet to try it, but I believe that there is a command if you get stuck and its /ref and it'll refresh the game, try that.

I taught Bellsprout HM cut.

then bellsprout level up after beat 1 of the pokemons of Erika and it wants to learn a new skill.

Cut is replaced by that skill.

I want to move back to the door, but I get stucked.

How is that a bug?

 

HM moves are forgettable. Just relearn cut

Move out where?, Or you mean you cant move out from the gym? If thats so it have to be some kind of bug with red