Ans.1. Yes, you should contact a local lawyer to contest your case. You have good grounds to contest the case. Firstly non receipt of legal notice. Secondly, there is no liability since a consumer case is pending. Thirdly, he has not obtained OC so far. And so on.
Ans.2. You can not get the case quashed as there is no provision in NI Act. On the other hand, you can contest the case forcefully and can be acquitted.
Ans.3. Possession without OC is not considered possession. All the more he has to provide all the amenities as agreed.
Go ahead with contesting both cases forcefully.
In NI Act complaint after framing notice under section 251 Cr.pc (Not plead guilty), get permanent exemption in appearing the case on each date of hearings being NRI.
Good luck.