Hi Venkatesh Yadav
First take the dump of Standard tables like PA-PSA,EG-ESG groupings V_001P_ALL & V_503_ALL & Personnel Actions etc...
* Test the Integration between OM to PA (Reporting manager,cost center updations)
* PA to TM (Leave Request Apply,Approval from Portal)
*PA to PY (Payroll process up to Pre DME,Form 16 generation etc....)
Morover SAP will give the Drabacks&bugs list while patch level updation please check the same.
Start updation from with BASIS team Developmrnt-->Quality-->Production (if it possible Clone Production)
Hope it helps,All the Best
Regards,
Murali.