Dear Karisma.,
First of the GSTR 3B and GSTR 1,2 &3 is no more links. The GSTR 3B is just based two months return form. Bcoz, The GSTN can't ready to GSTR 1,2 & 3. The GST liabilities received from the way of GSTR 3b and we file the return and paid the liability on the date.
So, Govt get their Tax amounts from the way of GSTR 3B...
GSTR 1, 2 & 3 is the exact return forms for Future (from July 17) return. We follow the return form as our Transaction based activities. It's one of the activity of URD purchases ll be shown in GSTR 2 form.
Finally (It's only my view),
I think the RCM related liabity is not Get back. Bcoz, the Tax amount is first add in Liability as Cash then Less as ITC (As per IT Depreciation and SB A/c)
So, Wait and see the returns as Reflected...