All of my BTC from my Stake account got transferred to some unknown address without my knowledge.
Can you post the Bitcoin address here in which your withdrawal was made?
Why there is not authenticity check when the user logs in from a different country in a day's time or even whenever he logs in from a different country rather than his home country.?
If 2fa is enabled on your account, then the 2fa code is required for accessing your account. Otherwise, Stake sends a login code to users email address whenever a user login from a new device or location. 2fa or the email code is also required for each withdrawal. Perhaps, your device has been compromised without your knowledge. Have you checked
your login sessions? Is there any unknown IP address and location on your session activity?