Who am I? Who am I without past memory? Who am I? Am I my memory? For example, I am hindu. I am engineer. I am Rajput.

Who am I without past memory? Am I my past memory? I am engineer. I am hindu.
I think that Theravada Buddhism teaches that there isn't a good answer to this question, that it's not a good question to ask.

See this description of Right View especially where it talks about "a thicket of views".

Also that things you might consider "self" (e.g. body, feelings, etc.) are impermanent -- and also (impermanent) is every put-together thing -- and so it's better not to view those as "self" ("self-views" are unsatisfactory or lead to suffering).

See also How is it wrong to believe that a self exists, or that it doesn&#39;t?