For straddle lever. Sit in a straddle with the legs at least at a 75-90 degree angle. They don't need to be much wider.
Place hands right in front of crotch. Lift heels off ground. I like prescribing 3 sets of 10 followed by a hold off the ground for 30s or 3 sets of 10 seconds.
You can also work inward and outward circles in this position.
Or simply practice them, shoot for 60s of total volume. Rest 15-30 seconds between attempts. Hold as high as you can so long as it doesn't start to drop as it should remain from start to finish at that height.
It is easier to work with an english handstand grip with the legs straddling the beam instead of with a side handstand like grip.
You can search for threads on front limber and back walkover and pullover.
Back hip circle is just a strong backwards drop with the head in. Look at your toes or the bar and don't throw your head out. Toes go forwards as shoulder go backward.
Start by doing it tucked, then piked and eliminating the pike so the body is hollow.