Steps:

Insert the SD card with FAT32 filesystem into your flight controller (FCU).
Download and install QGroundControl in your laptop.
Open the QGroundControl software. Open the Vehicle Setup tab and select the Firmware menu.
Download the modified version of PX4 by CopterExpress for the Clover drone. Download the latest stable version v1.8.2-clever.10
Connect your flight controller to your PC over USB.
Wait for the FCU to connect to QGroundControl
Select PX4 Flight Stack (Firmware Setup) in the right bar.
Check Advanced Settings checkbox.
Select Custom fireware file from dropdown menu.
Press OK and select the file v1.8.2-clever.10.

Steps:

After flashing, the parameters will be shown up, such as Airframe, Radio, Sensors, Flight Modes, etc.
Open Vehicle Setup tab. Select the Airframe menu.
Select the Quadrotor X airframe type.
Select the Generic Quadrotor X from the dropdown menu.
Return to the top of the list and press Apply and Restart button, confirm by pressing Apply.
Wait for the settings to be applied and for the flight controller to restart.
Go to Parameters. Setting the configuraions as stated in link 2.

Rebooting causes resetting, the airframe is reset. This can be due to the SD card undetected. Your SD card can be malfunctioning. Change another.