Jelq and curve

Can jelqing in a certain direction eliminate/cause a curve to develop in a cock?

definetely yes!
I used this method because my dick was really bent downwards like hell. After one year it is at least a lil bit more straight.

for jelqing, does it make a difference if you are cut or uncut? thanks.

I don't know first-hand, but i would think that the difference in "slack" would make it more likely that a curve might be developed or exaggerated through intensive jelqing for a circumcized dick. certainly my experiences based on the guys i've known would seem to bear that out. however, given that everyone is different anyways, i doubt that it would normally be a significant factor either way.