Is there a way to find the 'the last factory reset time' ? any logs or any other stuff like that? Please reply.
Yes, it seems there is a way to find out about the last factory reset -- provided it was followed by a Google account initialization:
- Go to the Google Dashboard, login with your Google account.
- Scroll to the section labeled "Android" and expand it (by clicking its title / the LGM [little green man])
- Check for the device in question
Associated, you will find a date of registry. That doesn't reflect the first time a device was added, but the last time the Google account was activated on the device. So if you activate your Google account following a factory-reset, this field is updated and thus reflects this point-in-time.