Cenvat credit

no this is not possible

No clear rule on this. The purpose of the scheme is to provide credit and not to deny.

If substantial you can seek clarification in wirting from dept. If no reply then avail. Risk exists.

You can utilise only that much balance which you have availed in your credit register after 01/03/2015.

If there is any balance in your register of before 01/03/2015, you can not utilise it.