Re: lumia 640xl only has 8gb of internal memory and windows 10 requires 8gb wiil i be able to upgrad
It requires a minimum of 8GB of storage on the device, not 8GB free storage. What that means is that devices that have only 4GB, which there are some but they are few, will not be able to do the upgrade. You will need an 8GB device or higher in order to do the upgrade.
I have a Lumia 640, also with 8GB of storage. I am already running the preview of Windows 10 Mobile, and it is working quite well for me.