1. Rockets apparently used to destroy floating bricks too, so it may be possible.
2. Maybe circumvent "Buried" if there is a hole in the terrain by Set Empty?
3. Could probably be done.
4. mirror1.dif exists in my copy but I think it came with AoT, not Blockland. It works fine but needs a relight and never shows you in first person. Strangely, it does show 1st person in Age of Time.