Gain tax on property sale

I am a non resident pakistan. I bought a plot in dha karachi in june 2014. The registration certificate issued by dha is showing three dates
1. Date of purchase 16 june, 2014
2. Authenticated date 23 june, 2014
3. Registration certificate issue date 28 july 2014.

I wish to confirm that which date is consider as completion of 3 years of my plot purchase to avoid gain tax
What is the rate of gain tax if i intend to sale the plot before three years and how it is paid.