WELCOME WELCOME!! I'm Blitz, one of the admins here so I'm absolutely available for any questions you may have! To answer your above ones:
1. AU's are normalized but relatively infrequent, as typically the boards aren't filled with them, but people are always able to make AU threads! They typically do not count towards a character's activity, but are always fun :)
2. To easily find your watched threads, you can click on "Forum" on the top bar, and then navigate to "Watched Threads" or "Watched Forums." Of note, this is on desktop, so lmk if you're instead talking about mobile! Also, when you reply to a thread, you are automatically subscribed to watching it!
3. I am admittedly not the best person to ask about coding LOL but we do have a coding guide onsite! You can find it
here if you haven't already seen it. Otherwise, I recommend joining our discord
here and asking more detailed questions in our coding channel!
I'm so excited to plot and rp with you!