Hello Vennela,
Below are the answers to your queries:
1) Could you please let me know how long a document which is archived is available in the Echosign server
A). The document is available until and unless, the sender or creator has not deleted it from EchoSign account.
2)Also how long a document is available after it reached the first signer until he signs?
A). The document link is active unless the sender has cancelled the document or provided an expiration date for the signers to sign before it.
3)What are the prerequisities (i.e what personal data to be disclosed) to get the user account in echo sign along with license?
A). To register for an account, the personal details required is shown in the below link for Global trial registration:
Global Trial Registration | eSign services from Adobe
Let me know if you have more questions.
-Rijul