Liability of Property Tax

Q: Background:

Person A has registered the property ( apartment unit) in March 2014 and Person B has registered the property (apartment unit) in April 2014. Please note that both persons have purchased different apartment unit from the same builder. You should note few points here about the builder. They are listed below
1. Builder has not completed the entire project ( pending items like Amenities) till date. Hence he has not obtained OC and Khata.
2. Builder has not transferred Khata to the individual owners since the project is not complete
3. Builder has paid the property tax till 2014-15 for the "vacant land"
4. The builder has not handed over the complete project to the association yet since he has not completed the entire project
5. Residents who have bought the apartment, have started living in the apartment.

Case

Person A visits the BBMP office and he was told to pay the property tax for 2013-14( along with 2014-15 and 2015-16) since he has registered the property in March 2014 and March 2014 is part of 2013-14 where as Person B was also asked to pay the property tax for 2013-14 irrespective of the fact that he has registered the property in April 2014.
The reason given by the BBMP is - "Building is ready since the builder has started registering the property from March 204 onwards. In this case, person A is the example. When person B tries to convince him saying he has purchased/registered the sale deed only in April 2014, BBMP officials says to contact /ask the builder to pay the property tax for the year 2013-14 in Person B's case.

With the above background and case , can you please answer the below questions to the point?

1. Does BBMP official makes sense in the case of Person B? Who is responsible to pay the property tax in B' case? Is it the builder or B?

2. As per the BBMP official's claim of building is ready by March 2014, why did they accept the property tax from the builder till 2014-15 for the vacant land? Would not have they refused the payment saying building has come up and they should be paying the property tax for the building and not for the land?

3. Can Person B take the advantage of property tax paid by the builder for the vacant land till 2014-15 to claim the benefit of not paying the property tax for 2013-14 for the apartment unit( since its mandated by BBMP for him to pay the property tax for 2013-14 also irrespective of the date of registration) that he had purchased in April 2014?