From an app developers perspective, what happens when I root my Android phone?

Question

This question was born out of pure curiosity and the lack of relevant material, I couldn't find on the on Internet.

My question is simple, from the perspective of an Android developer, what changes when I root my phone. For example, in Android 10 and later, Android restricted the access to Clipboard API, https://developer.android.com/about/versions/10/privacy/changes#clipboard-data.

Can I get around these restrictions if I root my phone ?

I read, rooting your phone gives you access to the bootloader, but what does that exactly mean, does it mean I can install any OS I want ? But most of the times, we are just installing some version of Android only, so are people forking the Android code and removing these restrictions in the code itself and then shipping their own versions ??

Also, when someone change the code(if that's what is happening), how does a developer know, which APIs will work and which ones won't.

I know these are extremely vague questions which are covering an extremely wide spectrum and might be hard to answer(if that is the case, I would highly appreciate if someone can give me todays a starting point where I can start researching this and can get a better understanding).