GSTR 1 not filed by supplier

Yes...

If supplier filing his GSTR-1 (with your bills) in subsequent months (on or before September GST returns or Annual return which is earlier) then You can claim ITC based on GSTR 2A...


Note: if above said October is Oct-19 then You can claim ITC on or before September-20 GST returns or Annual Return Of FY 19-20 if supplier filed the same period.

You Invoice will be reflecting in your FORM GSTR-2A in the month in which your Supplier uploads your Invoice in his GSTR-1. You can claim ITC once the invoice reflects in GSTR-2A. You can also apply the New 20% Eligible ITC Rule for claiming ITC.

Yes you can ................(assuming it's October 2019)