It benefit for new home loan (earlier flat sold)

Yes you can avail benefit of home loan interest & principal over second flat also...

At the same time you are entitled to get LTCG exemption u/s. 54 for the sold flat, but you should file return for AY 2019-20.

1. You can claim deductions towards principal repayment under sec 80C there is no restriction for the second house. In your case since you have already sold the property, there should not be any problem. 
2. Interest can also be claimed as deductions u/s 24(b) to the extent of Rs. 2,00,000. 
3. And explained by expert above the sale of a house to the tune of Rs. 42 lakhs will attract Long term capital gains and subsequently, if another house is purchased within a period of 2 years from the date of sale then the same will exempted u/s 54. 
Please correct me if the above solution has an alternative view.