Answer 1

End trigger would have been nice.

Answer 2

death zones are boxes drawn with the skull. Checkpoints are the blue flag. End trigger is the red flag, shift click enemies after placing to link them as the end-enemies.

Answer 3

i dont understand how people make levels without end tags. do you just assume the level magically ends? the game knows when the player is "done" and does him or her the favor of ending the play experience?