All done - very enjoyable but quite hard work for the end game.
Just a couple of loose ends for me from the initial grid. 10a - ‘poem that’s not advanced’ must give the 3rd and 4th letters of the answer. I know what it is from the definition, but how does that bit of wordplay work, please?
28d - I believe this is just an anagram, but ‘arises’ is then the anagrind. I’d have thought ‘arises’ would be more an indicator that the word is just reversed (in a down clue)?