Using :
Stick with Windows Phone 8.1 with interop unlock (registry access, sideloading). nokia lumia 520 custom rom work
Because the Lumia 520 has only 512MB of RAM, your options are limited: 🤖 Android (Project Astoria / LittleKernel) Android 4.4 (KitKat) : The most stable version found for this hardware. Performance : Very slow due to limited RAM. Functionality : Wi-Fi often works; cellular data usually fails. : Mostly a proof-of-concept for enthusiasts. 🏁 Windows 10 Mobile The Upgrade : Moving from WP8.1 to W10M. Using : Stick with Windows Phone 8