If a level is altered in a way that the gameplay is significantly affected or expanded, but the level itself remains easily recognisable (for example, blur's battle 1 edit) does that count as a remake or is that something else? I ask mostly because I'm curious.

I'm also currently messing around with an old level (not mine), but it's a test level so I don't think it qualifies for this.

And since you are accepting well known non-official levels provided the authour's concent is given, would it be allowed for someone to remake their own levels?