Your data is incomplete. So I rewrite the answer. 

You will be Resident (resident and ordinarily resident ) if 

 your status  was resident for any 2 years out of  10 f. Y preceding current f. Y. 

  OR

If you lived in India for minimum  of 730 days during 7 f. Y. Preceding current f. Y. 

If none of above condition is satisfied you will be Resident but not ordinarily resident .

And accordingly sec 195 will apply to you for that entire financial year. 

Date of execution of sale deed shall be considered as date of sale. 

No tax if total taxable income including ST capital gain is below the threshold limit. 

1. You will get resident status after March 2020 as you are treated as resident when in last financial year you are staying more then 182 days.

2. After december also bit shall be 20 percent only.

3. See it shall be considered from date of.allotment letter.

4. The capital gain shall be treated as income and on same slap shall apply. 

It's from the date you received the proceeds in your account. 

Yes it will attract tax 

At present you are holding NRI status, so sale is not advisable at present, Resume your residential status first.

Holding property for 3 years from date of purchase/sale deed, LTCG will levy, whcih can also be saved. NO exemption of STCGT.

Yes TDS will be deducted @ 20% 

Capital gain tax will be applicable on your property You don't reinvest the consideration to purchase some other property with in Two years from date of sale. 

1.  If you have decided to stay back in India permanently then you dont have to show the NRI status, you can proceed based on the aadhar card and other idn=entity proofs.

2. If you show yourself as a NRI then you may have to pay TDS at the rate of 22.5%.

3. Since the date of registered sale deed on your name, you will be considered as the owner fo the property.

If it is less than two years as on the date of resale then you may have to pay short term capital gains tax.

4. short term capital gains shall be computed as per the procedures.

The gain on a depreciable asset is always taxed as short term capital gain. The consideration or amount received by the seller on transferring or selling the asset. Expense incurred in transferring the asset, like brokerage or fee. The amount for which the asset was acquired

Illustration
In April, 2019 Mr. Rahul sold his residential house property which was purchased in
May, 2017. Capital gain on such sale amounted to Rs. 8,40,000. In this case the house
property is sold after holding for a period of less than 24 months and, hence, gain of Rs.
8,40,000 will be charged to tax as Short Term Capital Gain.