i imagine this can be adjusted to only allow for 2 speeds, due to it being a front derailleur, correct?

also, does anyone have a link to a left twist shifter similar to the shimano on the nova. all i can find is a 3 speed, i imagine that a 2 speed twist shift doesn't exist, or i'd have to adjust the derailleur so that it will not pull off the chain if i only have a 2 speed crankset and accidentally bump it into 3rd up front.
or i could always get a generic thumb shifter