first 360s - YouTube
So I finally landed a 360 at last. It looks so much uglier than I remembered it to be. Anyways, I noticed that I need to suck my knees earlier, which will let me push harder and I need to speed up a tiny bit more. My hands somehow are on the wrong side, which makes it look really awkward.. and I should suck in my knees during the spinning motion. It looks like I'm landing tail heavy, was it because I threw my shoulder a bit too high?
I don't see any real issues with your knees. Yeah you could have brought them up more and you should definitely throw a grab into that spin too, but it wasn't that bad.
The bigger problem I saw was your spin setup technique that relied entirely on your upper body and pre-winding just before you left the lip.
I didn't see any carving to create rotation.
It seemed to be all coming from your pre-wind and pop, which is fine once you get more advanced, but right now your pre-wind and pop are very rough and you're getting basically zero rotation help from your carve (or lack of carve.
If you carve correctly you won't need to pop so hard and the 360 won't look so forced by your body because your body is assisting with the 360, not create the entire rotation.
example here: The Secret To An Effortless 360 Rotation - The Perfect Carve Line
If you combine what you're doing now (pop+upper body rotation) with carving correctly, you'll find you don't have to pop as hard or throw the spin as hard with your body and it'll make it way easier to spin a smooth 360.
2) Land blind
You over-rotated your frontside 360 because you didn't spot your landing correctly.
Frontside 360s should be landed blind. So you basically need to be looking down/back uphill as you ride away. If you try to turn your head to look downhill you'll slip into a 540, which is what you did in the video.
Only turn your head to look downhill after you've stomped the trick and are riding away clean.