We went to Hong Kong and Tokyo with our DS when he was 10 months old. We took plenty of snacks for him, like raisins, rice cakes, dried fruit. We also took two sets of spare clothes in case of poo leakages! We took a couple of favourite books and a couple of toys.
We booked a bassinet, and although DS didn't use it much to sleep in (preferred to sleep over my shoulder) it did provide lots of extra legroom and space for DS to sit on the floor and play.
On each flight we were always sat next to another family so the babies just entertained each other and grabbed toys and snacks from each other too!
We used a sling for going through the airports and we also took our buggy so we had options! The buggy can be checked in at the gate before you board the plane and if you're stopping over they can arrange for it to meet you at the door while you wait for your next flight.
I won't lie, milk was a pain in the backside, we took cartons of milk and sterilised bottles on board, plus a bottle brush and washing up liquid so that we wouldn't have to worry about having boiled water etc.
With the time difference, we just slept when we arrived in Hong Kong as we were knackered and co-slept with DS. We just took him to bed when we were tired, and we all woke up at 2am Hong Kong time anyway, so we just got up, gave DS some milk and a snack and let him play for an hour, then went back to bed. We found the best thing was to feed him a good sized meal at breakfast, lunch and dinner, and if he woke in the night to go with the flow. It wasn't too bad at all, I think by day 3 we all slept through and adjusted to the time.