Things that happens in every BL manga/hwa/hua

I'll go first.Actually there's a lot but I don't want to say since I want to hear it from you guys
1.MC is always The Uke/Bottom like I have seen a lof BL and all of them got MC as uke
3.Nipple thing, collarbone thing.Like damn you Seme ,Uke just showed his nipple accidentally and you're getting horny tf. It's like "It's time to eat"
I'll leave the rest to you guys hdjdd I just wanna know