I think depends if the cuff is part of the knit or has been applied on, if applied on then yes potentially could be shortened by taking it off and moving it up, again this would depend on the structure of the knit in question and if the person doing the alteration has the right tools.

in a nut shell if its a cut and sewn knit maybe, if its fully fashioned (all one piece linked together) then i think less likely

yes