ST Registration Documents

I recently registered a private limited company for Service Tax on Online ACES Portal.

After registering, it requires to send the following documents:

(a) PAN card,
(b) Proof of address,
(c) Constitution of applicant at the time of filling an application for Registration,
(d) Power of attorney in respect of authorized person(s) 

Q.1 In what cases the power of attorney is needed and the format of the same.

Q.2 If the authorized signatory is a director, do we need a resolution also for the same? And also does the director has to be present while submitting ST 1 and collecting ST 2.

Q.3 MOA, AOA alongwith CERTIFICATE OF INCORPORATION are enough to describe the constitution.

Q.4 What documents need signature?
And the signature should be alongwith the seal of the company or without it?

Q.5 How many set of documents are required to be submitted?