Normally we use apps like Mobile Uncle or MTK Engineering Mode app to access this mode but I will be showing you various dailing codes you can use to access this Engineering Mode on MTK devices without using those apps.
Note
Not all MediaTek devices support these codes
Be careful of what you change in this mode, inappropriate action may brick your device.
To use any of the code below, open your dialer and enter
*#*#3646633#*#*
*#3646633#*#*
*#*#788378#*#*
*#*#1478963#*#*
*#*#36951#*#*
*#*#8838#*#*
*#15963#*
*#*#33#*#*
*#*#00#*#*
*#1949#*
*#1942#*
*#78837#
*#1942#*