#1
Apparently the boss ps-6 has a octave mode on it.

Would it be a suitable replacement for the boss oc-3 octaver?

I have already have the oc-3, if the ps-6 can basically do the same thing, i'll trade the oc-3 in.
#3
The Oc-3 is fairly rubbish, I've had it but now have an OC-2 and its much better but only for some things, it is by no means the best all round octave.

really depends on what sort of octave tone you want, the Octron is much better for most applications, digitech whammy if you want it kinda glitchy.