Have H1B approved petition,want to travel on H4B and later change to H1B

Hi,I am holding a approved H1B petition valid till 2016.However due to personal reason cannot utilize my H1B and want to travel along with my spouse on H4B and taking sabatical from my existing company.Want to know the below;

a) Can I get H4B stamped,do I loose my already approved H1B (not yet stamped)

b)If the above is Yes,then can I later get my H4B to H1B converted before the petition expires.Will it be a fresh stamping,COS or what exactly will be the process.

Request to please provide help me with the information.