“They” don’t have that. Most labellers are user made and people can subscribe to them or not.

I was interested until I learnt that the story is going to involve young Adam crashing on Earth and spending the next 20 years there. Don’t. For fuck’s sake.

Did you mean: He-Man & the Masters of the Multiverse

Feeds are aggregators that show you posts that fulfill certain criteria, such as mentioning keywords (which can include but is not limited to hashtags). They’re a lot more versatile than just hashtags. I can’t tell you why they chose the # symbol to represent feeds ┐⁠(⁠ ⁠∵⁠ ⁠)⁠┌

On your profile you have a following count, that’s where you’ll find a list of people you follow.

The key concept you want to look into is feeds. They’re as, if not more important than hashtags. There’s a feed called Following which is all posts from people you subscribe to.