This is a great question. I also see an increasing number of sweepstakes that include TikTok as a method of entry. We don't list many TikTok-only giveaways at the moment because TikTok does not have published guidelines for running a contest or sweepstakes on the platform. So, like some other social media, it can be a little more challenging to tell the validity of a contest.
However, like Instagram, they typically should use an exclusive hashtag for the promotion and provide official rules in the post or a link to those rules. If you're looking at giveaways on TikTok, check for those things.
I don't believe you need to have a fleshed-out account to win, especially if you're only using the platform as a method to get additional entries for sweeps that are hosted on Gleam and such. I hope that helps you out a bit! Happy sweeping and Happy new year!