How long can you keep an open can of formula? IF I keep the unused formula in the freezer, can I use it 2-3 months later?

You need to discard the formula milk after 2 months once opened up. Unless you didn't open the cover very frequently then can last until 3 months. It is best to discard as bacteria will grow inside due to the humid weather in Singapore and it is best not to risk your baby from getting stomach upset.