Can a person use a shop as his residence

This is your query: what are the remedies available to ‘A’.. Is there any Bye-law which supports his case and if not then under which Bye-law can the society not allow him from residing in his shop..

Being a member of the society, you have every right to inspect the books, can have a copy of bye-laws, and seek such clarification from the society itself as you are paying maintenance and has a right to seek information as a consumer.  It is their obligation to provide the reference on such bye-laws that bar residing in that commercial accommodation, after 8 years of such residing in the same manner without any objections in the past.

File RTI Application with a fee of Rs.10/- on line to the Suburban-Mumbai Authorities that approved the construction and to whom you are paying taxes and seek information as follows:

Information solicited. Please provide me the copy of laid down norms/orders/circulars/notifications/precedents that bar a commercial shop owner in a commercial complex, using such apartment as residence also.

The Society or its Managing Committee is not a sovereign bay.  They cannot take law into their hands. They need to take recourse to law even if alleged lapse on the part of A is causing inconvenience.

What is the basis / Bye-Law / Rule / provision of law under which CHS has permitted him to run commercial activity in the Society ?

If it was a commercial space as per building approved plan  then he can very well use this proeprty for commercial purposes.

He and his family members can utilise it for accommodation also after the business hours.

However they are not permitted to use the society wash room for their purposes on regular basis. 

The society, if decided to take any action, must quote the relevant laws in this regard before taking any action against the shopkeeper 

Well they have never objected till date.. But is there any provision where they can be stopped from objecting..

Since there's no objection to this so far, he may continue to carry out in the same way but he can prepare to confront the eventuality that may arise in future in this connection.