Thank you so much for the help.
I did contortion every day for two hours for months, and I progressed quickly-ish, and then I hit a glass ceiling. My flexibility stopped improving. (Though now I can do over splits cold, with absolutely no discomfort. lol.) I just barely sat on my head once or twice, and can still do advanced over splits. But I never progressed any more. For weeks or months I didn't progress. I'm currently taking a break. I wonder if I overdid it, and that's why I didn't progress. My back hurt everyday. I was born with natural flexibility, and took ballet for years as a little girl. I can do a chest stand cold...(yeah, I know I'm not supposed to do stuff cold...I was being bad) But now, after a break of a month or two, it seems like I can do the same moves cold that I did with a warm up when I was practicing everyday. Basically, my cold flexibility has improved, but my warmed-up flexibility isn't as good as it was when I was practicing. I don't understand!! I love contortion, sorry for the long reply, and thank you so much for your help!