I had some trouble understanding how building with the scripting backend IL2CPP is different from building with the scripting backend Mono in Unity. I tried to inform myself in the internet, but couldn't find the right answers for my questions. I know how everything works, but I'm just wondering if I have to take care of something special in order for IL2CPP to work properly with my game?

I'd like to know a few things:

• Do I have to change my code or anything in order to successfully use IL2CPP or can I just switch to this scripting backend and everything is fine? Can I also just switch back and forth?
• If it is that easy, why is IL2CPP not standard if it's more performant and harder to decompile?
• Am I likely going to encounter any issues with IL2CPP in Unity?
• Are there any restrictions with IL2CPP except for the target platform restrictions and the other small restrictions (linked here: https://docs.unity3d.com/Manual/ScriptingRestrictions.html)

I'd be happy if someone could help me understand this better. I hope you don't mind all these questions.