Interest principle of under construction deductable?

The home loan deduction can only be claimed from the financial year in which the construction is completed.

prior construction period interest can be accumulated and can be claimed from the f.y. in which property constructed or acquired

Interest can be claimed under section 24b from the financial year in which the construction is completed.
Pre - construction interest paid upto the financial year preceeding the year in which the construction is complete, can be accumulated and claimed in 5 equal installments from the year in which the construction is completed.