GSTP exam

i think, as per rule 83(1)(b), the sales tax practitioners need to appear for exam.

As per proviso to sub rule (3) of rule 83 of CGST Act:
Provided that no person enrolled as a goods and services tax practitioner shall be eligible to remain enrolled unless he passes such examination conducted at such periods and by such authority as may be notified by the Commissioner on the recommendations of the Council:

Hence to pass examination is mandatory.