Litterally, idk if I'm double jointed or if everyone can do this
So, I'mma gonna tell u how
But if it hurts, stop, don't break anything
I litterally just saw someone do this and tried it a few times and got it
It is not my fault if u dislocate ur arm or anything

So, when u can do this, u'll be able to put ur arms from in front of you, under ur legs behind u, then over ur head to back in front of you...

1 to make it easier, this isn't actually gonna do it yet, but it's what I did at first to get used to one step at a time
So,
1, y'know how a seatbelt goes in front of u?
Make a seatbelt with ur hands now
Ur hands should be like middle finger to the base of the other middle finger
If your arms are short, this is gonna be harder...
So, now, fold ur hands but keeping the middle fingers correct, if u need pics I'll do another chapter for steps with pics
But, now ur gonna put that seatbelt behind u
So, I use my right arm, but u can also do this with the left...
I'mma gonna instrucy with right arm, so if u wanna use ur left, just replace right with left (I can personally do both hands at this step, but I'm still practicing my left for fun)
So, now, make the seatbelt with the correct hands behind ur back with ur right are up
Now, ur left arm is going to lead here, so, put ur left arm up beside ur ear, like ur should would be by ur ear
Ur left elbow would be out alittle
Now ur right arm will just follow over ur head
It should be kinda natural
Ur hands would be more of going past ur arm pit rather than over ur head though...

Now, if u do this slowly, u might choke urself, so be careful

2 ur wrist will kinda fold a little here
So now, keeping the grip put ur right arm over ur left and now ur hands are in front of you! Yay!

3 now u can just easily step over ur hands, keeping the grip to put ur hands behind ur back...
This is harder now

4 now, ur going to push ur right wrist to the right until ur right arm is against ur back. Now u'll like put ur right elbow between ur back and left hand
This is very hard
After that, u should be in that seat belt position kinda, cus ur right arm would just like, go up

If u can or can't do this, plz comment, but also idk of this is normal or not...

Also, can u bend ur thumb over ur knuckles? Can u turn it to have the nail face the same direction of ur palm? Can u lay it flat on ur arm?
Is my thumb / wrist flexible? Or like, is this just weird? Or what?

Don't hurt urself trying this plz