return 3b

What do you mean by deposit cash in cash ledger?

1. If you are calculated your purchase and Sales related taxes after you get any liability then you ll be ready to pay tax. At the time you ll be deposit cash on cash Ledger...
After filing GSTR 1 and 2. Finally you get exact figure in GSTR 3. Then you ll be pay any balance Tax shortage...

2. Which month return..?!
If you can't save then it's not filed. So, you can file your GSTR 3B return....