You cannot be challenged if your status is set to 'away'.
The timezone is set to 'Coordinated Universal Time' which will affect the time set in your calendars and emails.
Challenges expire after 7 days after which it is forfeited and the challenger wins the match.
The challenger cannot challenge more than 3 places above their position.
Max Simultaneous Challenges: Default (one up, two down)
If you challenge and lose you will still gain a position.