To which department my case involved?

File writ petition before high court or Supreme Court, claiming your right to self determination 

At present where are you residing?  You have to obtain the caste certificate from Odisha Revenue Sub Divisional Officer.  The job will be given by an authority of a Department/institute/organization.  But not by the people whether they accepted your community or not.  It is not a question at all.  It seems like an academic query but not a real one.

It is difficult to understand your query. Firstly, it is not only the Assamese people that will refused to accept Bhuliya Community of Odisha as Assemese, as even Bhuliya Community of Odisha will refused Assemese people, so there is no discriminatory character as far as that Caste matter is concerned, as this is the same with all the other states practices on Caste, which is rooted in birth. As far as your job is concerned, if you are discriminated because of your Caste, you can always challenge it in the Court on the grounds of unconstitutional actions of the department concerned. But, I can gather from your query that the threat to your job is only your imaginations, and it will be premature to give you any concrete answer to that.