Sale to sez

Required reply urgently.

I am manufacturer in Gujarat.

I am selling goods to SEZ in Gujarat - what forms I need to take back from my customer in SEZ. Form I required or not?

Suppose I sale outside Gujarat -  whether I need to collect form I OR form 402 OR both.

When form I need to be collected -  in advance or later. If later - within what time?

Suppose my Mumbai branch is selling goods to SEZ in Gujarat. Whether Mumbai branch need to collect form 403 back from the unit in SEZ.