Hi Sukrut
I believe this is a Technical Upgrade.
If so once the platforms and DB versions are satisfied go ahead with the below steps.
1. ABAP objects and DDIC fixes with respect to the customized objects(14 day window to fix given by SAP)
2. Find and fix Unicode Objects
3. Remediation of all the Objects (Z Objects)
4. Unit Testing on each and individual Transactions in the Upgraded system.
This is the basic plan that we should follow.
Regards
Balakumar