To exit, simply press and hold the Power button for about 10–15 seconds until the device vibrates and reboots normally. Fastboot Mode OPPO A3s - HardReset.info

Press and hold the Power Button for a few seconds until the power off slider appears. Slide it down to completely shut down your

If your hardware buttons are not working or you are already connected to a PC for development work, you can use .

adb devices

on OPPO A3s:

Use this if your phone is working and USB debugging is enabled.

Learning is a journey filled with more obstacles than solutions due to OPPO’s aggressive security policies. While hardware key combinations and ADB commands work on devices from brands like Xiaomi or Google, OPPO has deliberately restricted access on the A3s.

If your goal is to flash custom ROMs or root your OPPO A3s, your best bet is to use with the proper MSM Download Tool. Alternatively, explore unofficial methods that involve unlocking the bootloader via an authorized OPPO account (very rare and difficult).