1. Since you have refused to accept their proposal for redevelopment of the property by demolishing it, you can remain silent, let them approach court with any case they may feel it fit.
Once the original owners have got the property mutated to their names and have been in possession and enjoyment of their respective portion of property ever since without interruption or interference from any external source, it is deemed to be that the property has been orally partitioned and to evidence the same, the mutation records and the document s pertaining to their possession and enjoyment would be sufficient to establish there was a partition among the joint owners.
Therefore if you do not want to accede their request then you can remain silent, if they take any action in this regard you can challenge the same ion the basis of the mutation records and other documentary evidences in your support.
2. If at all they are trying to demolish the house property where you reside, you can file a permanent injunction suit to restrain them from indulging such activities without following due process of law and in the same suit you can file an application for temporary injunction n the same lines till the disposal of the suit.
3. No, they cannot do so, it is your imaginary fear, shed it out and take legal steps to prevent them from doing so if you are scared about their threats.
4. you file a suit for injunction and follow it up regularly from remote place too.
5. No is the answer.
6. Court will not force you to sell it because it is your own property and enjoying it separately without being a joint tenant.
7. If the threat persist then you can give a complaint to the local police besides filing an injunction suit against them.