You can use some online device provider services like : browserstack I never tried it but check out : Run custom ROM on Android Emulator You can always borrow / buy an actual device.
To enable “install via usb” you have to insert sim card. After enabling “install via usb” remove sim card then it will work without sim card also.
Happens to my Xiaomi phone after updated it to MIUI 8. Took me hours to figure it out! Check the followings if you’re a victim too: Go to Settings -> Permissions -> Install via USB: Uncheck your App if it’s listed. Go to Settings -> Additional Settings -> Privacy: Check the Unknown Sources option. Finally … Read more