Since Android 6.0.1 is newer than Android 5.0, it falls within the officially supported window for standard operations.
A: Yes, downloading the APK for an app you are legally entitled to use is generally legal for personal use. However, distributing modified or cracked versions of the app is illegal and a violation of WhatsApp's terms of service. hot download whatsapp for android 601
Android allows manual file installation using Android Package (APK) files. Step 1: Enable Unknown Sources Since Android 6