i listened and watched to some recordings of "Prelude in C-Sharp Minor" and I observed that some use una corda, while others use damper. is it a combo of both? or is it u.c pedal, damper pattern? me? i dont know, that's for sure.
I am going to assume you are referring to the sostenuto pedal and not the una corda. You must use a combination of both the sostenuto and the damper pedals in order to convey the harmony clearly over the pedal tone.
nope, the very left pedal.