Does factory resetting the android smartphone erases all data from it?

NO...NOT AT ALL....

Factory Reset only deletes app data,user data and internal storage too.


But internal storage, contacts,text messages,etc.can be recovered by recovery software like easeus mobisaver.

For this I'll personally factory reset my phone and recovered all data.

NOTE:
1. FOR RECOVERY YOU HAVE TO ROOT YOUR DEVICE.

2. IT IS ONLY TESTED ON ANDROID.