Urgent basis - Need Advice before I purchase a plot.

Q: Hi All,
My Grand Father expired in 2006 and he owned a property 30*40 with 3 floors – Ground, 1st, and 2nd.
He was the sole owner of the property which he purchased almost 35 years before in Bangalore.
He got his will which stated that, Ground floor belongs to my cousin, First floor belongs to me and 2nd belongs to my other cousin. Now my cousin who is in ground floor wants to sell her portion of property to me after 3 years but I am worried if She has already sold that property to someone else or there is any legal issue happening between my cousin and her Mom on the property. The tax is not paid from 2005.
Questions:
1. How do I check if that property is still in her name?
2. Should her husband also be witness while purchasing the property because she done want her hubby to know about it?
3. How do I check if there is any legal issues on that portion?

Please help
Regards
Raj