It has been approved for 3 and up.
However, it has been successful with kids younger than 3 with supervision & assistance.
Yes, possibly even more efficient. Efficiency is measured on particle size and air exchange ratio. VixOne Nebulizer provides the smallest particle size available, while the Loli-O treat reduces stress/anxiety of treatment, providing a calmer child and an even higher air exchange ratio.
In a medical setting, no. However, moms and dads are free to re-use the Loli-O base as long as they can get it back from their little one!