I recommend keeping the magma stone you don´t miss anything. You get the TMs from Kristilline and save Amber but the most important part is, you can use Valor mountains main entrance without crashing the game.
That is not unfortunately not the right file.
The link below shows you how to access your save data and backup saves.
You can use your backup saves to go back to a previous save.
This should solve most problems you encounter.
This is not your save data. Here is a link on how you can access your save data and your backup saves. As long as you have backup saves enabled you can go to a previous save. You might lose some progress but at least you can play the game.
If you are really worried you can make a backup and try. It works for me without a problem just make sure you have the latest version and you should be fine.
As of v11 you can make multiple save file without switching the files around. Starting a new game should automatically create a new save file named game_2.rxdata (in your save file folder) assuming its your second playthrough.
Posting your save file might help people to better understand your problem.
The Zygard Cell next to Gearen Help Center was apparently moved somewhere else.
Try to avoid the main entrance to Valor Mountain it is possible but unfortunately a bit inconvenient.
Yeah you are right there is no indicator like a crack or something to signal that you can interact with the rock. The only indicator we get are shadows in the lava.
In v10 Carotos Mountain used the same "puzzle" but the solution was more obvious because each rock was located at the end of a path. I don´t remember if there was any other indicator.
You can create multiple saves by naming your savegame Game_2.rxdata or Game_3.rxdata etc. so you don´t have to delete the original. Alternatively you can just remove the original form the folder and store it somewhere else
I had the same issue when I fist played v11 the thing is you are not supposed to be able to go back to Gearen City before you get HM Fly an defeat the corresponding gym leader.
Later patches fixed this so just go back to Sashila Village and finish the story and the swapping issues should stop.
Yes you can just use debug mode go to Form and change it to 1.
The game uses the normal shaymin back sprite so you have to rename the sky-form back sprite to 492b_1.