Backside 50/50, they are soo fun to do, way easier to lock for long one than frontside.
Hardflip, I never tried to learn but 6 months ago a friend who can do them very well showed me how he did them, I tried (for the first time) and understood the motion. Fast forward to now, it's been 6 month since I tried one (forgot about it and there are some other tricks that I wanted to learn). A kid at the park asked my if I could do a presure hardflip, I said no but tried a normal one just for fun. It went well, after a few tries I stuck one. It's funny how some tricks can be a battle to unlock and some can come super easy. I'll def work on them next session.