Michael:
With brevity in mind, I'll give you the quick and dirty answers as I see them (i.e., IMHO):
1) YES!
2) Maybe. If a cable is designed specifically for that purpose, I don't see why it can't, with varying degrees of success, do just that.
3) Sometimes yes, sometimes not. Good audio cables tend to improve sonically with age...unless the materials physically oxidize (i.e., conductors and connectors) and/or the dielectrics disintegrate (chemically or physically) or are damaged.
4) YES!
5) YES!
6) YES!
There have been several threads on this very subject here, so you might wanna do a site search.
Everyone uses something different, some buy 'em, some make 'em themselves. There are hi-dollar audiophile-grade cables, low-priced junk, and everything in between. While there is a difference, we're dealing with the Law Of Diminishing Returns here: it takes exponentially more dosh to get an infinitessimal improvement in sound quality. I'm currently using Monster, having had good results using them for my hi-fi rig, but their instrument cables exhibit microphonics (i.e., tap on the cable and you can clearly hear the thump through the amp!), which is unacceptable to me. People brag about Pete Cornish's stuff, others use MIT (a good audiophile cable), while others get Canare or Mogami wire and make their own. Alembic used to make their own years ago, but are apparently way too busy to bother these days. Listen for yourself and make-up your own mind. Bear in mind that old A chain is only as strong as it's weakest link axiom.
Everyone else: please feel free to chime in here.
Cheers,
Kevin