Eligible or not

The National Academy of Customs, Indirect Taxes and Narcotics (NACIN) has been authorized to conduct an examination for confirmation of enrollment of Goods and Services Tax Practitioners 

The GSTPs enrolled on the GST Network under sub-rule (2) of Rule 83 and covered by clause (b) of sub-rule (1) of Rule 83, i.e. those meeting the eligibility criteria of having enrolled as sales tax practitioners or tax return preparer under the existing law for a period not less than five years, are required to pass the said examination before 31.12.2018 in terms of second proviso to rule 83(3). The examination for such GSTPs shall be conducted on 31.10.2018 from 1100hrs to 1330 hrs at designated examination centres across India.

Hence Exam conducted on 1.10.18 is only for STP (Sale tax practitioner) & TRP who is practising for not less then 5 yrs . 
This was told earlier by Pankaj sir...

Clear and detailed explanation by Vinod Babu likes it