Check out this tutorial for Samsung Galaxy S4 mini i9195T to hard reset your phone. You can try this tutorial with other Samsung Galaxy S4 mini. But I cannot guarantee that If this procedure will work.
Hard resetting / factory resetting your phone will solve the following issues:
1. If you forgot your pattern lock
2. If you forgot your gmail account
3. If you forgot your password
4. Apps that automatically force closing
5. Stuck in Logo (sometimes does not work if the firmware is totally damage)
NOTE: Performing hard reset will erase your data.
To hard reset:
1. Turn off your phone
2. Press and Hold VOLUME UP + Home Button +Power Button simultaneously. Do not release until you see "RECOVERY BOOTING" in the screen.
3. Just wait until you see the Android System Recovery
4. Select wipe / factory reset, press Volume rocker to navigate and press the POWER Button to confirm your selection.
5. Reboot your phone.
Note: Some variant of Samsung Galaxy S4 Mini does not show recovery booting. So if you see the Samsung Galaxy S4 Mini Release the buttons
Note: If performing hard reset did not succeed, you need to wipe the cache first in the android system recovery before performing wipe / factory reset.
I hope this tutorial helps you.. If you have any question just drop a comment.