No. This is highly risky. A compromised Android 6.0.1 device can intercept SMS messages and keystrokes. Use a separate, newer device for financial transactions.
Yes. If you back up to Google Drive (while still on Android 6.0.1), you can restore that backup to any newer Android phone. However, if your backup is local (stored on the phone's internal memory), move the folder to a PC before switching. will whatsapp work on android 6.0.1
Ensure your chat history is backed up to Google Drive by going to Settings > Chats > Chat Backup > Back Up . will whatsapp work on android 6.0.1