Re: Best software for recording mixes/ legality of posting mixes
There's no real "official standard" to those sorts of things, you just sort of get a feel for them over time. People do them differently, anyways.
I've heard some remixes which sounded nothing like the original, I've heard some remixes which made one or two basic changes (adding an intro, removing a breakdown) and I would consider it an edit. I've heard some "remakes" or "covers" which I would call remixes.
Now, from my personal perspective on the examples you gave:
- if you take a remix and replace the drop with your own drop
I'd call this an edit.
- take a remix and combine it with an acapella
I'd call that a mashup.
"ID" just means that the track is unknown, or the selector is unwilling/unable to share what it is. "Re-edit" is probably just a redundant way of saying "edit", heh. Remode is just a remix. Sometimes people just like to call it something else to put their own creative spin on the title. ("Respray" is another one.)