Whether review of the orders passed under this act is permissible? If so under what circumstances revisionary powers

In terms of Section 2(99) “Revisional Authority” means an authority appointed of authorised for revision of decision or orders as referred to in section 108
The review authority either on his own motion or based on the information received by him or based on the request of the Commissioner of State Tax or Commissioner of Union Territory tax, could call for and examine the record of any proceeding, and if he considers that any decision or order passed under this CGST Act, or SGST Act or UTGST Act, by any officer subordinate to him is:
(a) erroneous in so far as it is prejudicial to the interest of the revenue and        (b) illegal or improper or has not taken into account certain material facts, whether available at the time of issuance of the said order or not; or
(c) in consequence of an observation by the Comptroller and Auditor General of India, he may stay the operation of such decision or order for such period as he deems fit and after giving the person concerned an opportunity of being heard and after making such further inquiry as may be necessary, pass such order, as he thinks just and proper, including enhancing or modifying or annulling the said decision or order. For the purposes of this section, ‘record’ shall include all records relating to any proceedings under this Act available at the time of examination by the Revisional Authority.

(ICAI FAQ PUBLICATIONS 06-09-2017 Revisional Powers of Chief Commissioner or Commissioner: FAQ NO. 14)

Whether the Appellate Authority can enhance the penalty or fee? If so under what circumstances

Yes, the Appellate Authority could enhance the penalty. However, an order enhancing any fee or penalty or fine in lieu of confiscation or confiscating goods of greater value or reducing the amount of refund or input tax credit shall not be passed unless the appellant has been given a reasonable opportunity of showing cause against the proposed order.

(ICAI FAQ PUBLICATIONS 06-09-2017 APPEALS AND REVISIONS: FAQ NO. 13)

What type of order could the Appellate Authority pass? Whether Appellate Authority could refer the case back to Adjudicating authority

The Appellate Authority may pass such order, as he thinks just and proper, confirming, modifying or annulling the decision or order appealed against. The order shall be in writing giving details as to determination. The Appellate Authority shall, along with its order under section 107(11), issue a summary of the order in FORM GST APL-04 clearly indicating the final amount of demand confirmed. However, the Appellate Authority does not have power to refer the case back to the Adjudicating authority that passed the said decision or order.

(ICAI FAQ PUBLICATIONS 06-09-2017 APPEALS AND REVISIONS: FAQ NO. 12)

Whether parties to an appeal could seek adjournment of the hearing

Yes. The Appellate Authority may, grant adjournment of personal hearing if sufficient cause is shown at any stage of hearing of an appeal, grant time, from time to time, to the parties or any of them and adjourn the hearing of the appeal for reasons to be recorded in writing. However, no such adjournment shall be granted more than three times to a party during hearing of the appeal.

(ICAI FAQ PUBLICATIONS 06-09-2017 APPEALS AND REVISIONS: FAQ NO. 10)

Whether entire amount of tax, interest, penalty, fine or fee has to be remitted before preferring appeal

For filing appeal following amounts shall have to be remitted:

Demands which are not contested Entire amount of such demands (tax, interest and penalty) shall have to be remitted
Demands which are contested a sum equal to 10% of the remaining amount of tax in dispute arising from the said order shall have to be remitted

(ICAI FAQ PUBLICATIONS 06-09-2017 APPEALS AND REVISIONS : FAQ NO. 7)

Is there any time limit for filing appeal

Yes. Time limit to file appeal before Appellate Authority, for an assessee (person aggrieved) is 3 months from the date of communication of the order. Whereas in case of an appeal filed by the department on the basis of the directions by the Commissioner shall have to be filed within 6 months from date of communication of the decision or order.

(ICAI FAQ PUBLICATIONS 06-09-2017 APPEALS AND REVISIONS : FAQ NO. 5)