Probably fake
Seems to be a short video about a guy called Oleg Polovski, but there's no other documentation about him. As usual in these cases, it's a very low quality video.
Humans can have a "tail", but not with bones, not movable. Usually they're removed.[Nature]
It's in the wrong place. If it was real, his lower spine is sticking out of his body, about 6" from where it ought to be - which would cause lots of problems.
There's some info in Portuguese, translated here.
Cf. "Are Some People Really Born With Tails?", on Today I Found Out.
(, Fri 3 May 2019, 23:28, Reply)