@Sebastien_Mendoza, when you need to create screenshots, use the PRINT key on keyboard, this will copy all pixels of your screen as a Bitmap in your clipboard. Then paste in Paint and save as PNG. If Citra has a builtin method to take screenshots I’m not aware of it yet.
Cheat codes modifies running game memory. That is dangerous by nature. We don’t have the game source code and we are guessing about the meaning of values in its memory. If you got that after trying a cheat code don’t insist. Chances are they don’t work for your ROM version.
I have encountering these issues before. I only can conclude that not all PokeMon games sharing the same title are the same code. There are small differences that result in different memory locations. For example, different translations may have different memory locations, and same cheat code doesn’t work.