Complex sentence: In 2020, the HDB flats are currently under construction and it will be completed in between Q2 and Q3 2020, and this station will open if the flats are full with residents in the HDB flats.
Split into simpler sentences: In 2020, the HDB flats are currently under consrtuction and it will be completed in between Q2 and Q3 2020. And this station will open if the flats are full with residents in the HDB flats.