20 buttons hidden in the colourful cacophony. Can you find them all? (Very difficult)

Jed's gallery of buttons is a find-the-button style map. There are 20 buttons hidden in the room. A few of them are straightforward, but most are very difficult. If you find all 20, tell me what time you got! :)

Adventure mode. Feel free to do everything within your vanilla minecraft power to find them. F5 is allowed but frowned upon.

There is no redstone, hoppers, or anything else unintuitive to make the buttons unfairly difficult to find.