What is State Bench or Area Bench

The Government, by notification, specify for each State or Union territory, a Bench of the Appellate Tribunal, exercising the powers of the Appellate Tribunal within the concerned State or Union territory.
Government shall, on receipt of a request from any State Government, constitute such number of Area Benches in that State, as may be recommended by the Council

(ICAI FAQ PUBLICATIONS 06-09-2017 Constitution of Appellate Tribunal: FAQ NO. 25)

What is jurisdiction of National and Regional Benches

National and Regional Benches shall have jurisdiction to hear appeals against the orders passed by the Appellate Authority or the Revisional Authority in the cases where one of the issues involved relates to the place of supply.

(ICAI FAQ PUBLICATIONS 06-09-2017 Constitution of Appellate Tribunal: FAQ NO. 24)

What is the Constitution of National Appellate Tribunal and how the same is constituted

The Central Government shall on the recommendation of the GST Council by
Notification constitute Goods and Services Tax Appellate Tribunal (hereinafter referred to as the Appellate Tribunal) for hearing appeals against the orders passed by the Appellate Authority or the Revisional Authority.

(ICAI FAQ PUBLICATIONS 06-09-2017 Constitution of Appellate Tribunal: FAQ NO. 21)

How to compute the time limit of 3 years (from the date of the order of lower authority) / 1 year within which the order shall be reviewed

Where the said decision or order involves an issue on which the Appellate Tribunal or the High Court has given its decision which is prejudicial to the interest of revenue in some other proceedings and an appeal to the High Court or the Supreme Court against such decision of the Appellate Tribunal or as the case may be, the High Court is pending, the time period spent between the date of the decision of the Appellate Tribunal and the date of the decision of the High Court or as the case may be, the date of the decision of the High Court and the date of the decision of the Supreme Court shall be excluded in computing the period of 3 years, where notice for revision has been issued.
Where the issuance of an order under sub-section (1) is stayed by the order of a Court or Tribunal, the period of such stay shall be excluded in computing the period referred to in clause (b) of sub-section (2).

(ICAI FAQ PUBLICATIONS 06-09-2017 Revisional Powers of Chief Commissioner or Commissioner: FAQ NO. 20)

Which are the other orders or decision that a Revisional Authority cannot review

Following orders or decisions cannot be reviewed by a revision authority
(a) order has been subject to an appeal under before Tribunal (under section 112) or High Court (under section 117) or Supreme Court (under section 118); or
(b) the period of 6 months as specified under 107(2) for preferring an appeal by department before Appellate Authority has not yet expired or
(c) where more than three years have expired after the passing of the decision or order sought to be revised.
(d) where the order has already been taken for revision under this section at any earlier stage.
(e) revisionary order passed under this section [i.e. section 108(1)].

(ICAI FAQ PUBLICATIONS 06-09-2017 Revisional Powers of Chief Commissioner or Commissioner: FAQ NO. 16)