• Want vacant shop from tenant

I have one shop which is given on rent to our family friends son for doing business by my father.Their is no agreement executed for the shop it's just verbal communication between both family. We also take rent in cash. The light bill was paid by tenant The shop given on rent in the year 2001. When in the year 2009 we want get shop back from them.They said we will vacant in the next year. In the year 2010 we don't take rent for 6 month to make him defaulter for the rent,on the basis of that we think he should vacant the shop. But unfortunately he make a case on inter pleader suit on us. saying we are not legal owner of shop. he had rent agreement with other which is owner of shop. He also claim that we are damaging his business and asking for money illegally from him .
In the court he claim for who is actual owner. The rent he claim in court is INR2500/- pm. But actual rent we are taking INR 8000/-pm.Whom he was calming as legal owner of the shop, is actuality son of seller of property to us. In the year 2013 we got tenant sales tax certificate through RTI. In which he has mention us as actual owner of property.Currently case is ongoing . Now his sister in law and owner( whom he claim in suit the court) executed sales deed of the shop.
Facts and figure of property :
1) We have buy property from father of claim owner( as mention in inter pleader suit by tenant) 17 years ago.
2) Light bill,water bill,and tax property in the name of us.We are paying regularly.
3) In RTI for sales certificate in sales tax department,showing us as owner of property .
4) property in Bihar

Now my questions are as below :

1)How we can get back shop form them.
2)What legal action should be taken against tenant.
3)We can make challenge of sales deed made by his sisters in law and owner (who is real owner as claim by tenant in suit)
4)What legal step need to prevent both parities to occupies said properties.
5)can we claim forge case on his sisters in laws and fake owner?
6)what should be procedure for stop his sister in laws for false claim of property.