Do these stick to your cotton dresses - are they a satiny finish?

they're a sort of in-between finish, but mostly matte. They do NOT stick to any dress I wear them with - cotton knit, broadcloth cotton, or silk.

Do these make any noise at all when you walk (i.e. when thighs rub past each other)? I have a different brand & they are too loud to wear.

They make minimal to no noise. They are soft and highly comfortable. If I were to order another pair, I may get a larger size but that is personal preference.

Are the length in these just above knee or mid thigh?

I guess it depends on your leg length. I'm 5'3" and the inseam on my Jockey skimmie is 7" (size small) but with a lot of stretch, so when I pull it on it hits me about 3-4" above the knee, a little longer than mid thigh. However, they're very easy to pull up a little more if you're wanting to wear them under shorter dresses and still very comfortable.

Where is the size guide?

I couldn’t find one so I ordered a size small (I wear a size 6 dress). Big mistake. They’re so skinny I can’t even get them over my big toe. There was no way I could get them up over my legs and hips. I really should have sent them back but was too lazy. I wouldn’t buy them if I were you.