How many days is a power of attorney valid?

1- if "the agent" to whom power of attorney has to be given, if he apply for power of attorney instead of principal and the agent writes and prints the power of attorney and gets the signatures of two witnesses. then in the end he sends this document to the Principal to signs this power of attorney, is this power of attorney valid ? 2- can an agent act for the Principal, before the signatures on power of attorney ? to get the e-stamp paper, to pay the fees and to write the content of power of attorney ? 3- if the two witnesses live in the country of the agent and principal lives in another country , where he signs the power of attorney while witness had already signed the document in another country, should the witnesses be in the same country where the Principal is living so that they can witness the principal ? 4- should the witness sign the power of attorney after the signatures of the principal or the witness can sign the document before the principal ?