Lyrics and WIP translation

I love Puryu's latest song, but I'm struggling with the following points. Any suggestions? Am I missing anything?
  1. The ending to verse 1 seems to say that they'll talk about a festival they enjoyed but they'll eventually realize they never went.
  2. Verse 4, line 1 "anata" is going out, and line 3 he'll come home. Does kaeru of line 2 refer to going out (his world is not at home) or to verse 3 (his world is at home)?
  3. Who is doing what in verse 4, i.e., who is dressing and getting a mike, and who is listening to whom?
  4. What actually is the song about? We have this hint in the comments: "お祝い。"