I use crotchet thread and it works fine, doesn't tangle in my hair or anything. Then again i've only used threading overnight to stretch my hair, not as a long term protective style so i don't know if the crotchet thread would tangle if it's left in for a long time. It doesn't pull my hair or anything tho, i like it so far.
It actually doesn't take as long as it looks, the first time i did 10 sections, after that i did 16 sections and my hair came out straighter than with 10 sections. It took less than an hour to do the 16 sections so definitely quicker than blow drying or roller setting for me!
I did it on freshly washed, shrunken hair and it got it blow dryer straight anyway so no, your hair definitely does not have to be pre-stretched.
My advice would be to cut the thread first, i moved faster when i did that rather than having to pause to cut a piece each time. Also i don't make a knot first, to me that just takes up unnecessary time and i dont have an issue with it pulling out without the knot so i'd say just skip that step.