In soloQ, I'm Plat IV 0 LP (not because I'm hardstuck, I haven't played a single ranked game ever since I completed my plat promos).
In flex, I'm Gold IV 0 LP (same reason as soloQ).
In 3v3, I'm currently Bronze I 60 LP and I still have 1 more provisional left to go, meaning I can reach Silver IV 0 LP if I win a game then lose one, or if I lose the last provisional and do the promos. You probably see at this point what I'm trying to get at.
In TFT, I only played the provisional games and I'm Bronze IV with 70 LP. If I keep ff-ing at 10 minutes, will I hit 0 LP before demoting, or if I lose a game at like 2 LP, I'll demote and won't stop at 0 LP? I'm not sure because there aren't promos either, so you may get demoted before being stopped at 0 LP.