GST Lilability

Business started 1st of July 2017
GST Registration number taken on 15th of July 2017.
From 1-15 July goods purchased with GST paid.
All lying at stock on 15th of July.
..
Now have 2 questions
1) is any manner to claim ITC on this stock as Tax invoice not have my GSTIN

2)
if say stock (100 + GST 12 )
and my sale Price is 115 with GST.

so how much GST I have to pay. ..
..
115/112*12 = 12.32

But I'm not able to claim ITC on stock then

As profit added is only Rs. 3 if no ITC is allowed.
Then GST payable =3/112*12 = 0.32
Can I do so.
If ITC not allowed.

Note. . Rate of GST 12%