Here are some answer based on personal experience:
- How big is the legroom in Y on the 737-800 ?
32"
Source
- What is the IFE in Y on 737-800 ?
Personal TV screen
Source
For 1-1½ hour flight, it just shows some episodes of TV, some music, etc.
- Through check from HKG to the final destination even if transiting in CGK ? Do I need to retrieve checked bags in CGK (vs. transiting in BKK to a domestic Thai destination where you only see the bags at the final destination) ?
Not any more. Your bags will be checked through Hong Kong to the final destination. You don't have to retrieve them at the baggage carousel in Jakarta.
- Realistically, if I am entering Indonesia at CGK and immediately connecting to a domestic flight, given that GA International and Domestic operate in the same terminal building (albeit in different sub-terminals), how much time does it take to reach the domestic boarding gate once I leave the Secure Area ? (I'm a foreigner but do not require any visa to go into Indonesia.)
You now don't have to leave the secure area. There is now a special "transit lane" that goes direct from international to Garuda domestic, especially for Garuda passengers transiting from an international fight to a domestic flight. It's a 5 minute walk up some stairs, through some doors, etc.
By the way, if your final destination is Surabaya (SUB), there is a direct Cathay Pacific flight from Hong Kong to Surabaya. Based on my previous experiences flying both airlines, it would have to be a pretty amazing Garuda fare for me to choose Garuda over Cathay.