I hope it's obvious I was replying to another problem, possibly Leomann, I can't remember.
I don't understand the last problem discussed so have no idea. If you can't log into your main account, I don't know what you're trying to change. But I realise I'm coming in on the end of that one, so feel free to ignore me....
I do know I eventually found options covering yahoo email addresses, following from the link I put above. But my problem was different - simply trying to get into the account.
I just tried to unlink the accounts I didn't ask to be linked and found that option to unlink is again not available.
There are also all sorts of 'not allowed' points which probably explain some of the problems above.