One person can only apply for one bid in an IPO. Your application amount will determine whether you are applying as NII (or retail investor) or RII. You are a NII if you submit a bid amount greater than Rs 2 Lakhs. If the bid amount is less that Rs 2 lakhs, you qualify as a retail investor.
It is prohibited to apply multiple times for the same Demat number. However, you may bid multiple times in an IPO under the name of family members. All family members must have their Demat or PAN numbers.