My ceo says first complete the project then he will given relieving date

Hi I work in company X as associate director( which is not a post like other companies directors, we just manage multiple projects if given like managers, train people who can be moved to any project any time, then we do coding by ourselves and then again train new people). My appointment letter(when i joined company as lead has notice period mentioned as 3 months. I have resigned and serving the same. But now company says you are part of management group and have to serve 2 year notice as per hr policy(i have not agreed to or signed any contract which states anything like that nor anything was explained to me or I have not given any consent on this or no mutual discussion or agreement is done which explained me all this) suddenly. But I told as per my notice period mentioned in appointment letter I will server only 3 months. Now my ceo who is my boss also, sent mail that i have to first complete the project and then releving will be done as per policy. I don’t want to have any issue and server my 3 months notice and leave. But i am afraid he will not give releving letter