For the ABC meme: F, R and Y? :D
F - What’s the longest you’ve ever been in a fandom?
I have been in the Sonic fandom since I was too young to remember. It's something I've brushed in and out of over the years, but it's always been a presence in my life.
R - Which friendship/platonic relationship is your favorite in fandom?
There's so many good ones to choose from! Maybe random, but I love the friendship between Klavier and Trucy in Ace Attorney - united in trolling Apollo. Oh, another Ace Attorney one! Replaying the first trilogy made me really appreciate the friendship between Phoenix and Maya. Now those two are a great example of how you do a purely platonic relationship between your main male and female characters.
Y - What are your secondhand fandoms (i.e., fandoms you aren’t in personally but are tangentially familiar with because your friends/people on your dash are in them)?
Gonna be honest, I have a lot less of these now, because I'm much quicker to mute series I'm not interested in seeing and y'all are so good about tagging your posts to keep stuff I don't want to see off my dash. But there's some series that I don't follow but still like seeing on my dash. The first one that comes to mind is Sailor Moon. Despite reblogging a lot of content from it, I'm not that familiar with the series, I just like the aesthetic. I did read the manga and didn't retain any of it and I would like to watch the older Sailor Moon anime one day, though.