Hi @ayeowch ,
I followed the procedures outlined in the forum to restore to the stock eMMC. I use the provided eMMC to microSD adapter, plug it in my usb card reader, restore the image file, place the eMMC back on the PCB.
It's not the first time I had to do this, ever since I switched from the microSD to an USB stick, the B1 frequently stops working.
Which also answers your question wrt to the stock microSD