I would start with the very first Red line bus in the morning, then do the Green bus because it leaves from the same place (Star Ferry Terminal). The Pier 7 cafe is a nice place near the Big Bus stop for sandwiches and other light meal options. Then you'll need to take the Star Ferry to Kowloon and walk a bit to get to the Blue bus route. If you have any energy or time leftover, you can do the included harbor tour and/or the night bus tour. I would not get off at any of the stops on any of the routes. If you do, you'll have to wait up to 30 minutes for the next bus, and then there's no way you can do all 3 loops.

Yes there is

By bus or Uber.

You cannot see it on the bus you have to be by the water

Unfortunately mot

All three

It seems to be for all of them. When we got off the bus the representative from big bus was there and he pointed us the right way. Really friendly guy, great service. Did not check what level ticket we had

Yes, we run the full service during these period

There is a Big Bus app that you can download where is easy to find a bus stop and check where the next bus is using “real time tracking“ The Blue Route may pick you close to the ship terminal. I took the Red and Green route. ;-) We did not buy it online.