There's no advice I can give you on how to survive 20 hours of flying. I can tell you that on a flight from LA to Tokyo, everyone closes their windows. Everyone. Almost immediately. Even though my flight left at 1pm, all the passengers seemed to want it to be nighttime as soon as possible.
My theories for this include:
a. as you're flying over the Pacific, there's really nothing to see
b. it's insanely bright. sky, clouds, wings of the plane: nearly pure white. it hurt my eyes.
c. it's a 13 hour flight to Tokyo, and people wanted to sleep as soon as possible.
d. it's easier to watch the tv screen when it's dark.
I had a window seat as usual, but I was peer pressured to close my window (and directly asked by the guy two seats over, less than 20 minutes into the flight), so the point of having a window seat was lost. The guy right next to me went to sleep an hour and a half in, with his tray table down, meaning I was stuck. What an asshole. I should've spit in his water. He also slept for a good 9 hours straight. I hated him.
Fast forward to the Singapore hotel: the Swissotel. It's a European hotel in Singapore, and therefore totally confusing. It took me a few tries to figure out the details of how the room even worked. The lights only come on if your keycard is in a slot by the door. The lightswitch isn't there though- it's over by the bed. And it's not a switch, it's a button on the alarm clock. The minibar is stocked, but the bottle of water costs $7.50 and the tiny can of Pringles is $5. I'm starving, but won't stoop to such blatant robbery. The air conditioning is on the Antarctica setting, and it took me a day to figure it out. Silly me- the controls for it are ALSO on the alarm clock. As is the 'do not disturb' light.
Which thankfully I managed to turn on before crashing asleep around 3am.