1) The backup can only be made to Google drive, you cannot create a manual backup to a location of your chosing

2) The backup is created in a secret folder that cannot be accessed by the user

3) The backup is deleted if you delete your account. (not much of a backup, eh?)

4) You can only create per-channel exports, but this won't export the entire chat, it will export up to ~12MB of recent media, and ignore the rest, silently. WhatsApp would only share the last 40 messages of a 4-year-old chat because the last few messages contained a few images.