Yes! Soft drinks, beer, and wine.
Absolutely! Keep in mind there will be an open bar and a bunch of "20-something" year old guests requesting all different genres of music.
If your invitation says "and Guest," then yes, if not, we would prefer if it was just you.
Semi Formal. We want everyone to feel comfortable, so if those shoes are too high or that top button is too tight, then let it all hang loose.