Well if that's the case I can find twelve changes but one is in a clue that's already been changed ... which doesn't configure with the rubric that twelve separate clues must be changed ...
I think I've finished but I also don't have enough changes. Don't really understand 11ac/5dn - changing a 'u' to an 'i' in five down doesn't fit with the instructions. Have I gone wrong somewhere?
11 ac is an anagram of 2 words in the clue.
Yes, I could change the n in 13 dn but have already changed the first letter - so that doesn't fit with the instructions that twelve separate solutions need adapting.