A decision in principle creates a soft credit search on your records, once you decide to proceed with the mortgage offer then they perform a hard credit search.
There are no charges for a decision in principle from UK mortgage lenders, but it can be a lot of paper work to go to each individually.
What I would highly recommend, and what I did myself, is to ...
If i availed the new home loan on ready possession flat and the interest paid upto 1.50 lacs, can i get the tax benefit ?
Yes you can designate this as first house and get interest benefits of Rs 1.5 lacs