Hi @Mohit Vadhera ,
maybe it's a misunderstanding:
The 200 US$ credit is for 30 days only. After the 30 days the 200 US$ are "gone" and can't be "reset".
Also it's not possible to extend the 30 days period as far as I know.
Source: https://azure.microsoft.com/en-us/free#all-free-services
(If the reply was helpful please don't forget to upvote and/or accept as answer, thank you)
Regards
Andreas Baumgarten