There is (currently) only one living version of the Mastodon code base. It could be forked in the future, but it hasn’t been.
There are other ActivityPub microblogging platforms (Friendica, Mbin, Pleroma, Threads if you count it) which users could also be running, and from the point of view of users it shouldn’t be obvious what any other given user you interact with is using, but that’s not got anything to do with Mastodon pull requests.
I too am addicted to likecohol.