#2
there are a lot of mixed reviews about those such cables. some work well, some are crap. i have a UX1, and it works great for what i need. the pod farm software is no where near as bad as people make it out to be either. granted, it isn't the best amplifier simulator available, but it works fine if you're just practicing, and with some EQ to remove some fizz, it sounds perfectly fine in a mix.

if you don't want to splash out the extra cash for a UX2, look at the GX or UX1. they're the same thing, except with less inputs. if you're only looking for guitar, the GX will do you fine, it's a fraction of the price of a UX2.
I deeply regret the 6661 in my username. Siiiigh. Damn you, 14 year old me, you edgy little bastard.
#3
I see line 6 ux2 lets you plug in microphones. Does that give me the option of setting up karaoke on PC with that?