Rcm in GSTR3B and GSTR1

Sir

I request you pl help-

I filed GSTR1 under QRMP

I have purchse invoice of 26 march 21 and LR of transport is of 27 march 21 (under reverce charge) I received goods on 1april 21 with delivery invoice of transport for Fy 20-21,

 so reverse charge mai invoice kis month mai banega march/april.    itc of reverse charge ka credit kis month mai le sakta hu .   invoice under reverse charge, GST1 of march 21 main upload karna rah gaya he to usko kab upload kar sakta hu.  Rcm ka payment gstr 3B of march mai or april mai kar sakta hu ?  Such condition RCM credit kab le saktahu