To answer your questions,
1. Reception is full day but there is an option for half day on Wednesday. I think initially they may get tired but should adjust after a few weeks, and they will probably tend to sleep earlier at night time and for longer.
Even at nursery class, there are many kids attending full day and a lot of kids have given up their nap. But for those that still need to nap, the school will bring out mattresses and let them nap for about 20-30mins.
2. There are many mix kids and different nationalities at HLY so I wouldn't worry about English not being her first language. Some kids are more fluent than others and so long as she can understand and communicate, then she will be fine. I even know one kid who had very limited english to start with and he has made a lot of progress so far.
As for mandarin, they start with basic greetings and learn mandarin songs at nursery level. At the CNY concert, I heard the reception kids singing more complex songs and recite some poems, but because I don't speak mandarin I'm not really sure of the standard.
I know at primary level they will start to teach Mandarin in three groups depending on the child's level (something like expats, mandarin parents, local parents who know mandarin etc).
I've heard that HLY mandarin program is much better than ESF, but I know ESF are improving theirs now and introducing mandarin lessons every day at primary.
3. The teachers are really nice and great towards the kids. If the kids are upset/crying, they will take care of them and give them a hug until they have calmed down.
The teachers really focus on each individual child's ability so they are not pushed to do anything that they would struggle with, but at the same time encourage them to take part.
It's a tough decision to make. If we lived on HK island I think we would have definitely chosen ESF all the way. But since we are in the NT there are no ESF kindys and HLY is the closest school for us.
You should have a better idea after you have visited ESF.