Is it necessary to send my child to pre-school at 2-3yo? If not is there any disadvantages? Like hard to catch up the syllabus compare to others. Thinking to send her directly to K1.

Well I think some of the advantages would include social skills, independence and team work. And of course, there are academic and occupational benefits that can be had in the future. That being said, alot of us didn't go to pre school at such a young age and we turned out just fine. We eventually picked up the same skills at 4 or 5.