How can we verify or check if brokerage firm are also involued in trading as another business?

Is it possible that brokerage firm can or may have its own trading section?

Are there are any restriction or policies from SEBI for brokerage firm to not to indulge in trading to prevent conflict of interest or miss use of client money for their own benefit.

Usually a brokerage firm would have declared about this on the account opening forms if they trade prop or not. No restrictions on prop trading by brokerage firms.