If some employer files H1B visa for someone in India as employer.

The case clears the lottery but Visa is denied before the visa interview without the knowledge of employee in India.

Does employee in India has legal rights to ask his employer to provide information about why the visa denied ?

Your question uses confusing terminology.

I'm assuming when you say the "lottery" you are referring to the H-1B cap? The USCIS has not had to go to the lottery system for several years now. The petition was denied?

If so, it is usually one of three things: (1) the position does not qualify as a professional position requiring a minimum of a 4-year bachelors degree; (2) you don't have the required degree or (3) the company does not qualify (financial, etc.)

This is more of a labor-employment question, but I would think that since the petition is filed and signed by the company, the potential employee would not have a right to know, but certainly should be told why.