IS RCM APPLICABLE FOR FY20-21

No , applicable on all Goods and services notified by the GOVT .

Is RCM on p&l  expenses applicable ?? 
n if yes then which are those?

Regarding RCM GOVT has issued some notifications , that you have check on CBIC web site / GST / Notification section .
For example notification 4/2017 C.T (rate) dt 28/6/2017 for goods ,notification 13/2017 CT (rate) dt 28/6/2017 is for services . like wise just check other notification also till date.
All expenses mentioned in the notification where you have to pay GST under RCM.