I am also in the similar position building Plus 2 floors on the existing ground floor at chikkalsandra.
Can you pls send me the details,pictures at globalsupplychain1@gmail.com
This will be helpful.

I am unaware of 5 years option.
But you can pay the property tax online from any place in the world.
I live abroad and use this method to pay the yearly tax.
Paid my tax for 2012-13 yesterday.