Here are some responses to your questions:
Challenge to Construction Activities: You've already taken a positive step by obtaining a stay order to prevent further construction. If you believe that allowing the construction would prejudice your interests, it's essential to continue pursuing this matter in court. Your lawyer can file an application for permanent injunction or any other appropriate legal remedy to prevent construction that may affect the valuation of the property.
Status Quo of Property: The existing status quo of the property can be an important factor in partition cases. You should document and present evidence in court to support your argument regarding the depreciated superstructure.
Notice to Co-Owners: The fact that you issued a notice and the co-owners did not object to the ongoing construction may be relevant in court. Your lawyer can use this as evidence to establish that they were aware of the construction activities.
Property Demarcation and Auction: If demarcation of the property is not feasible, and if you believe that a fair division cannot be achieved, you can request the court to order the sale of the property and distribute the proceeds among the co-owners as per their shares. Your lawyer can file a partition suit for the sale of the property.
Contesting the Case Online: Courts in India have increasingly started using online platforms for case management and hearings. Depending on the specific court and its procedures, it may be possible to participate in the case online from Chennai. Your lawyer can guide you on this and help you set up any necessary online appearances.
Lodging Complaints: If you suspect wrongdoing or conspiracy by the other co-owners, you can consider lodging complaints with the appropriate authorities. These could include complaints related to property fraud, criminal conspiracy, or other relevant offenses. Your lawyer can advise you on the specific complaints to file and where to file them.