If I delete 1 Apple ID (email address) will the same email addy become available to use again? I have my own AppleID ("Bob") but I don't use this email addy "Bob" anymore. I want to add my current, daily used email addy ("Jim") to my ID, or better yet, make it my only AppleID and delete "Bob". BUT...
I already used "Jim" for an AppleID for an older friend who had no email address, so set it up for him on mine, "Jim".

My older friend now has an email address ("Ivan") so can I


add "Ivan" to his AppleID, make it the primary email address, and then delete "Jim" from it? Or...
delete his AppleID and create a new one for him "Ivan" knowing he would lose his minor purchases


And most importantly, this would all be pointless unless:
- will deleting/removing "Jim" as linked to my friend's AppleID then make "Jim" available for me and no longer registered to another account?
The short answer is "Yes".

If you go to https://appleid.apple.com/ and log in the "Jim" AppleID. You should start by adding the "Ivan" address to the "Jim"  AppleID then make it the primary email address. Confirm that it works for logging in. Now delete the "Jim" address from the now "Ivan" AppleID.

Repeat the above for the "Bob" AppleID with the now freely available "Jim" email address.