How to achieve factory-reset or bootloader mode for Flywheel (Glorystar Nebula rf3288) tablet without buttons?
For your device you should use a touch based recovery as you don't have any buttons. If you don't found a pre-compiled recovery for your device, look for another recovery or compile your own. You can also try to use this library to compile the recovery. Once you've got your recovery follow these steps.

Enable Developer mode in Settings.
Turn on OEM unlocking.
Connect your phone with USB cable.
Allow computer to access ADB.
Now execute the following commands...

Reboot from ADB to bootloader.
adb reboot bootloader


Should reboot the device to fastboot mode.

You might need to know your unlock code.
fastboot oem get_unlock_data


You have to send this code to the OEM and they should give you another code.

After that you can try to unlock the bootloader.
fastboot oem unlock bootloader your_code_from_oem


This step is necessary for Motorola devices, but not sure about others.

Then you should flash a recovery.
fastboot flash recovery recovery.img


Make sure you're flashing the correct recovery.

Then reboot into recovery.
fastboot reboot recovery


This should boot up the touch based recovery.

If you're done with all these steps then you've successfully unlocked your bootloader and flashed a custom recovery on the device. Now you can wipe the device including the OS.
Note: when you lock/unlock your bootloader your userdata is automatically wiped. If you don’t want to flash a custom recovery that’s fine, just simply unlock and relock the bootloader.