Claiming 54F by selling US stocks

Trying to understand how the dynamics work when I buy an under construction flat (where say the builder demands 70% since construction is close to complete).

Planning to sell US stocks and claim LTCG exemption. I believe if I sell stocks within 1 year of buying the flat and the construction competes in 3 years, this should be doable.

1. Since this is construction linked, do I sell stocks in one go and keep the money in CGAS(Capital gains account scheme).

2. Do I have to bring the money back to India mandatorily?

3. If I take a loan of say 50%, can I still claim 54F on 100% amount? I've seen many folks doing this.

Looking for experts to chime in or folks with personal experience.