Very nice orchard. I've heard people tell of yellow fruit that taste like lemon called "thai gold". Grower in US got plant from Vietnam back in 2019. Perhaps that is what you have. By the way your English is excellent so long as you don't speak too fast. Thanks for sharing your efforts with us.
I heard Australian Yellow Isis is self fertile so it needs external pollination. As you said, there are many bees in your farm, so maybe they did the work for you. I also have that variety but it is still not flowering.