If you notice any software malfunctions with your Vivo Y21L android device, you're most likely required to download and flash stock ROM firmware on your Y21L to permanently correct the software errors you noticed on your Vivo Y21L. And when you load stock firmware on your Vivo Y21L using any Qualcomm flash tool, your Vivo Y21L will be reset to factory defaults settings and by that, definately, your UserData will be lost including contacts, messages and others.
If your device has been bricked and want to unbrick it, you will need to pay closer attention to the tutorials contained below here.
Vivo Y21L Stock ROM Firmware Download Link(s)
1. Vivo Y21L_PD1309F_EX_A_1.7.1_LA_BR.1.1.3
How to Flash Stock Firmware On Vivo Y21L
1. Download your Vivo Y21L stock ROM firmware from the link above.
2. Extract the Vivo Y21L Firmware you downloaded from the link above onto a folder on your PC.
3. Download and install Qualcomm android device drivers on your PC. You may skip this step if you have installed Qualcomm drivers on your PC already otherwise, download Qualcomm drivers here
4. Now, choose either of the tools listed below here to load the stock firmware on your Vivo Y21L.
Note
1. Each of the tools listed above contained step by step guides with illustrated pictures on how to flash stock firmware on your Vivo Y21L.
2. If your device is bricked already, I recommend that you use Tool Studio eMMC Download Tool or QPST QFIL.
3. If you require any further assistance, simply drop your comment detailing the issue(s) and I shall help you revive your Vivo Y21L, if need be.