Bhupendra,
Let me first suggest you post this question in the Apptio product community using the link below. That forum will expose the question to product experts and practitioners:
https://community.apptio.com/communities/apptioproducts?CommunityKey=746e8816-0dae-489a-8b34-98a9ce69ec2d
There is a technical limitation in the planning tool where you need to have a baseline currency (one). And it should be the same one you use in Cost Transparency. Once you have the baseline currency you will be able to add other currencies with exchange rates, but the concept of a currency baseline may be a technical constraint to your question.
There are no limitations to how many times you update exchange rates.
Hope you find this answer helpful
------------------------------
Juan Jose Jarillo
Customer Success Advisor
Apptio
Davis CA
(650) 430-5358
------------------------------