Trending @Infosys; Can HR update last working day if manager says?

I was assigned to project 1 month ago and I put papers 2 days after my manager assigned me some work. He told me to work along with someone and said you will have to support until the deployment happens, This is a new technology for me too and I am not able to understand code much.

We have worked out with HR for releasing me in 30 days so currently my last working day is 22 April. If I don’t perform during these 30 days can he postpone my last working day or cancel it?