Section 54F applicability

Capital gains arise on transfer of capital asset.
Sec 54F APPLICABILITY IS IN THE FOLLOWING CASES :
1. land and residential unit sale consideration to be utilized for construction of new house property within a tenure I.e. within a period of 1 year before or two years after the date of such transfer purchased or within a period of three years constructed .
In your case it qualifies. But what is that inherited land.

In my home town, my father and mother have few open plots with them, they may gift any time in near future, unfortunately if any of them pass away without doing gift or will deed, as a legal heir me and my sisters will inherit those open plots. 

I had bought a residential plot 20 years ago and I may not settle in Bangalore where my plot exists, so I may have to sell the same and construct residential apartment at home town in that inherited/gifted plot.

Will my whole CG gets exemption if I do as stated above.

Obtain a power of attorney.

Deduction Amount - Net Consideration's Full Amount is invested. In the situation of investment of the full amount of the net consideration in construction/ purchase of a residential house, then the complete amount of long term capital gain can be exempted u/s 54F.

Deduction Amount - Net Consideration's Full Amount is invested. In the situation of investment of the full amount of the net consideration in construction/ purchase of a residential house, then the complete amount of long term capital gain can be exempted u/s 54F.