Last Date to take credit of Gst refund for FY 2017-18

The GST law requires that every claim for refund is to be filed within 2 years from the relevant date. So in the case of Exports made in FY 17-18, refund should be filed till FY 19-20.

As per my opinion, there is no time grant in this case due to Covid-19 pandemic.

As per Section 54(1) it's Application for refund can be file before expiry of 2 years from relevant date .

Yes grace time period is being extended in this case due Covid-19 pandemic.
As per Circular 137/07/2020 GST , under s.no. 6 , the timeline for any compliances required as per Sub-section (1) of Section 54 falls during the period from 20/3/2020 to 29/6/2020 the same has been extended to 30/6/2020. (Can refer Notification 35/2020 CT)

Hence if expiry of 2year falling between the said period be furnished till 30/6/2020