If a nominal code name, number or type is changed, this will automatically update in the rules when you next re-sync to your accounting file.
A account code can only be deleted in Xero or QBO if no transactions have ever used this code. So in this instance the rule simply wouldn't run as there are no transactions to recharge anyway.
If a code is archived, the rule will run as normal until all required transactions have been recharged.
If you need to change any of your rules to send costs or revenues to a newly added code, you can do that manually by updating any existing rules or creating a new one. See this helpful article for more information on how to create new rules.