2. If he refuses, can I appeal in the court against him?
3. If the owner himself wholeheartedly give me an amount, can I accept it? Is it halal for me? Awaiting for your reply.
بسم الله الرحمن الرحيم
(1&3) After staying for a long time in a rented house or shop as a tenant, the tenant does not become the owner of the house or shop. Thus if the owner of the house of shop asks to vacate it then it is necessary to vacate it without receiving money. It is not lawful to demand a huge amount for vacating the house or shop. And it shall be an oppression to take help from the court. However if you vacate without taking any compensation and the owner gives you some money happily then it shall be allowable for you to take.
Allah knows Best!
Darul Uloom Deoband