I have several noob questions about Linux on mobile

1. Why can you brick android phone by installing custom ROM. But such thing can't happen on x86? Or how likely is that. From what I read it is because it doesn't have bios and you can overwrite phone hardware drivers how true is that with recent devices? And I assume it is impossible to recower from software bricking?
2. Is that true that on Halium kernel distribution you can't use universal packages (flatpak, nix, snap, appimage), only precompiled for its specyfic system only? Is there any bypass of that to use something like apk like on android? Or are there any disadvantages to use it apart from EOL security.
3. Is there any good list how to start with Linux on phone? List of devices (probably oneplus 6, pixel 3a, fairphone 4), distros (probably Ubuntu touch, mobian, postmarketOS). The smoothest experience, preferably with dual boot.
4. Is there some recomended tablets to test with Linux mobile? It seems preferred way for me considering calling, camera and other issues which are on Linux mobile. Is recomended devices from postmarketos tablet tab?
5. Why battery life is worse on Linux than on android, I watched some reviews and they complained about short battery life.
6. I watched someone run Linux distros by clicking on android quick settings tray and it opened Linux desktop, but it was not mobile. How it is called and is there a way to run it with plasma mobile?
7. Is porting for newer devices getting easier with time or is getting harder?
8. How is process of jailbreaking with locked bootloader done? Can it be automated?
9. Is there megatread or some wiki with some basic question like these?

Thanks for answers. Sorry for long text.