1) Everything sounds really good. Love the many bubbles, especially the bubbles at ±1:25 that seem to follow the rhythm. That change in speed at 1:40 was wacky but fun.
2) I am never able to make repetitive background not annoy me. You seem to have put enough interesting sounds on top of it to make it work :D. Sounds very mystique, I like it.
3) I like the change at ±1:45 from one theme to another. Though they are quite different, they match nicely. 'Burst into Worlds' sounds really good.
4) I love Odd Ode! A really cute song.
I would say that your mixing and quality is really good. From the first song I ever heard from you, I knew you were very skilled. Keep up the good work :)