Capital gain account

the exemption u/s 54 can be taken only if the house is being purchased one year before or within 2 years after the transfer took place.  so in your case you should get the possession on or before Dec13 as for under construction flat the time limit is 3yrs from the date of trasnfer.,

In case the Capital Gains could not utilised on or before the due date of filing the I-T return, then the entire Cg is requried to be deposited under the deposit scheme & the amount can be withdrawn from the account for the puepose of purchasing a new flat within 2 years or for under construction flat within 3 years from teh date of trasnfer.so you can definitely withdraw the amount of 6lacs from the deposit scheme.

any balance remaining to the deposit account,  then tax @ 20% wud be requried to paid on the Capital Gains remaining unutilised.