it's possible to install arcpad on nokia lumia 820?
I'm not familiar with the lumia and the Windows Phone 8.1 operating system, but the system requirements for ArcPad are:
for or windows mobile. ArcPad Help MOBILE
And for windows ArcPad Help Windows
My initial guess would be no, since the CPU is not on the list of supported software.
But sometimes it's worth testing anyway, if that is you only option. Make sure you have a good backup before you do though. By the way, we typically use windows laptop/tablets, but have also used it on Trimble Yuma 2, and other GPS devices with the windows os.
I've been trying to install ArcPad 10.X on a Lumia 640 XL running Windows 8 and have had no luck at all. I just don't understand why ESRI wouldn't want to support newer Windows phone operating systems. Windows Mobile 6.X is ancient and the hardware running it is very slow.