ITC related query

you need to reverse the entry bcz your seller must have mentioned your transaction on B2C type in GDTR-1 return not in B2B. Hence it is not possible for him to give the credit and just bcz he didn't mention in on B2B type it must have not auto populated in your GSTR 2B form. As you have claimed it in your GSTR 3B it may lead to a potential mismatch bt 2A and 3B at the time of annual return.

u can claim it but check that u satisfy the sec 16(2) of cgst act. if not satisfy .u just reverse till march 2019 

you have to reverse it , since GST number is not mentioned , you won't get credit

If all the conditions mentioned in Sec 16(2) of CGST Act are fulfilled, then u are allowed to take ITC even in case of any mismatches......

Main condition of section is that you should have copy of tax invoice as per GST laws.
Tax invoice is incomplete in your case as it has not mentioned your GST number.
Hence Section 16 is not satisfied.

you will have pay this amount along with interest in DRC-03

by the virtue of section 16(2) it seems i can avail ITC on goods purchased.

The Following two main condition of this section is fulfilled -

• Possession of tax invoice or debit note issued by supplier
• Tax charged on such supply has been actually paid to the government

request vendor to give revised invoice adding GST No. and then no need to reverse GST.