I do use my right thumb on F'. I was just wondering how some people are able to do left index with thumb gripping on F face because it just doesn't work for me. It's very awkward for my hand and the S slice moves with it. I don't know what finger is supposed to hold the S slice in place...
My lunhui is normal sized cube. It is smooth, extremely sturdy and nearly impossible to pop even at gratuitously loose tensions. I can't say anything about the Lingyun, but I recommend the Lunhui a lot.
do you mean like....F2L algs?
because pretty sure you have to learn OLL/PLL algs, unless you're cool and generated your own or do it completely intuitively.
if F2L no you don't have to memorize any, but it doesn't hurt to look to see if there's ways to do cases you feel are awkard or you can do better with
If you can only physically turn the R and U faces of a cube, there is no way to change the relative corner permutation. The cube is unsolvable. Disassemble and repair the puzzle.