If you have access to any simulator like HYSYS, you can verify the hydrate point. To avoid start-up hydrates across the chokes, it is usual practice to dose hydrate inhibitor upstream of the choke.
Double isolation valve is a good engineering practice for high pressure systems and not a requirement by any code. Some operators do insist double isolation for all 300# pressure rating and above though 600# is more common.
In your case, you need to evaluate whether drains and vents under...
