Hi Priyanka,
What about the Account determination ID(AD ID) that is assigned at the contract account\contract level.
Using AD ID, you can segregate the different types of customers at the master data level and as well at the transaction data level.This is best practice and is the most cleanest approach from a reporting prespective as well.
AD ID is a configurable field and you can use it to have a separate combination of Company Code\AD ID\Div\Main Tr in EK01 and Company Code\AD ID\Div\Main Tr\SubTr in EK02.
Now with your second query-Are you talking about adjustment reversals (EA21)?
If so, I think so the old VAT rates will be shown in the adjustment reversals.
Hope it helps...
Thanks,
Amlan