How much screen time should be allowed per day on mobile phone for 2-5 yr olds?

If it were my child, I'd definitely limit usage and keep it to a bare minimum. I'd rather them run around in the mud and explore nature than let them sit for hours with the tablet at such a young age. Studies have shown that prolonged use of mobile devices can lead to detrimental health issues in children because of exposure to microwave radiation (MWR). Also, it can also ruin their eyesight if they stare at the screen at a close distance for a prolonged time.