HI @MarcusWong-9726 ,
Please find answers inline.
How to manually cleanup the ADFS config in Active Directory as we have no access to the corrupted ADFS nodes anymore?
All information related to ADFS is stored in local config database. The only thing you need to clear in AD is the machine account and service principal.
Can we configure the new ADFS server farm with the same Federation Service Name as previous corrupted adfs server farm?
Yes. You can use the same federation name. Make sure to have the correct DNS pointing.
Can we reuse the previous service account that was being used by corrupted adfs server farm?
Yes. Make sure you remove the old SPN's added (if delegation is being used) and add new SPN's to the service account.