(NOTE: I'm new and don't know how to get this to the right category. The category selection menu only has this as an option.)

Ok, I know Ubuntu Touch isn't really new, but I have two questions: I have an older Google Pixel 3a and a Samsung S6 that I wouldn't really mind upgrading to Ubuntu Touch. First, is there any Ubuntu Touch port for the Samsung S6, and if not, why not? Honestly, I would much rather install Ubuntu Touch on that device instead of the Pixel. Secondly, what happens if I don't like Ubuntu Touch/it doesn't work for me? How can I go back to the original Android 12 operating system that is currently on my Pixel 3a?