#1
We have studio monitors that we want to plug into our interface.

Will guitar cables damage anything? Could we use them? Or are speaker cables necessary?
#5
You don't want speaker cables for studio monitors. Studio monitors are powered, meaning they have a power amp built in. They take a low level input. Most will accept either mic or line level.

If your monitors have XLR ins and your interface has XLR outs then use a decent XLR cable. If they don't have XLR but will accept balanced 1/4" then use those. You'll get the best noise rejection that way. Otherwise, if you have to use the unbalanced 1/4" connections then any good shielded cable should work fine, including most guitar cables.

Speaker cables are unshielded two-wire cables with large conductors. They're designed to carry high current signals which aren't very susceptible to electromagnetic interference (it takes a HUGE magnetic field to put a dent in a signal that's already high current). They're terrible for low level signals that ARE highly susceptible to interference.

Guitar cables are coaxial shielded cables with a single small center conductor. They're specifically designed for low level signals, and are good at suppressing electromagnetic and RF interference. They also have a high natural capacitance, which makes them terrible for use between a power amp and a passive speaker.

XLR and balanced 1/4" cables are shielded cables with two small center conductors, each carrying an equal but opposite phase copy of the signal. This is the reason they're better at noise suppression. If they pick up any noise then, theoretically, it should be picked up equally by both center conductors. The receiver circuit inverts the phase of the signal on one of the center conductors, putting the two signals back in phase with other but inverting the phase of any noise picked up on that wire. Once the two signals are summed together the noise will cancel out, and only the original signal will be left.