Pls advise me the steps of how to request it and whether there is a special form or not? Is one week before the master hearing is enough and should I apply to petitions to both the judge of the immigration court and EOIR too? Kindly outline the procedures.

1. you must be removable (and the judge must deem you so at the hearing)
2. you must qualify for "voluntary departure"

Wait for the master hearing first, but gather all evidence that would prove you'd adhere to an order of removal and why you wouldn't be eligibable for "voluntary departure". If you're not familiar with the complex issue of immigration laws, you will need an immigration attorney or research the laws thoroughly yourself.

Good luck!