why does it say tiktok is restricted?

cus your parents blocked it

Stay in school.

See the little hourglass! This would indicate that it is probably a time-based thing and you have exceeded your allocated allotment for tiktok use. I don't know how, I don't know why,I'm just pointing this out as an additional clue.

You have parental controls on your phone, limiting your tiktok time. Maybe whoever set it is trying to tell you that you’re on tiktok for too long