How can I tell the version of os in my mobile?

kishan answer:

The steps to check your os version may vary based  on the  device (sometimes depending on your version, believe it or not!). Below are general instructions that should work for most Android devices.

1. Open your device's settings.
2. Look for an option that says About Device, About Phone, or something similar.
3. Find your Android version on the list of specifications.