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.

It has nothin to do with independency. My fren's kids went to playgroup from young. But still struggling at social skills even now at K2. If you do self teach at home, it will be even better. bonding! I personally seen cases around me, starting self teach at home and proceed k1, no issue in catching up. For immunity wise, it all depends. No such thing oso as u can be immune to things like rotavirus or even hfmd. Immunity starts from baby. over protective, no good. that is my point of view :)