2yrs son carpooll wit ath 2yrs boy who always have flu everyday, is car purifier/car ioniser/car ozoniser works to protect my son frm d virus?

Flu vaccine. The best ways to prevent illness from influenza virus is to get the flu vaccine every year, avoid direct contact with those who are sick with respiratory infections, and regular hand-washing. I am not aware of any car air purifiers that help to prevent people from getting sick from respiratory viruses.
No. The only way to avoid the virus is to avoid exposure to it.
Unlikely. By sharing such a small space, your child is at risk for catching illnesses from his friend. If you can avoid them sharing toys, drinks, or snacks, perhaps the exposure will be a bit less. Fyi, "flu/influenza" is a serious but seasonal illness... It is not likely that the other boy has "the flu"; more likely a string of routine colds.