Internal Team Transfer at Snap and Promo Difficulty

I have a great L3 offer from Snap, but I'm not sure if the team is in an area I see myself working long-term. How hard would it be to internally transfer to another team after a year or two? I'd ideally like to work on an ML, product, or data infra team. Also, how difficult are L3->L4 and L4->L5 promos? What does the promo cycle look like?