I'm currently working with the content blocker Extension which works just fine for Safari. But does anyone know if it can also be applied to Chrome, if so how?
Another question I have: Is it possible to block an app, with the content blocker Extension or some other way
From the Apple's documentation:
So it is not possible to block Chrome requests via Content Blockers.
For the other question you have, you can enable or disable any content blocker extensions from Safari's settings. Check here for more information.
If you are asking for a solution which blocks the apps, there are no way to programmatically do this in iOS (there may be some ways for jailbroken devices), at least to my knowledge.