All links are dofollow by default. To see if it's a nofollow ,type ctrl+u for page source then ctrl+f and type in nofollow if you see a rel="nofollow" that indicated that your link is not a dofollow
No, I don't think so. Because you can't share the links. People can't stop scrolling once they're on TikTok it would be very challenging to get their attention to visit a site.