I have two questions as mentioned:
1) I have to maintain requirement 63 for billingaccountrelease in billing output, so do I maintain it at access sequence level or at output procedure level and whts the difference?
2) Difference between INVOIC01 & INVOIC02?
I think you mean LV61B062. Purpose is to avoid to print the invoice before the document is released to accounting and the payment terms start to run. This is in the output determination procedure.
The requirement in the ouput pocedure will stop the output to be populated when it is not met.
The requirement in access sequence checks if a specific condition should be checked at all. You could check that you want the output to be determined for a specific condition (e.g customer/payment term ) only when you are in a certain country.
INVOIC02 is the sucessor of INVOIC01. It is a new version. If you want to check for details check we60.