Diverted will be non-blank if the flight’s destination has been diverted from where it was originally scheduled.
Filed_time is when the flight plan was entered into the system (which is usually a few hours prior to the planned departure time).
Filed_departuretime is when the flight is planned to depart.
Route is the list of navaids that the flight is expected to fly, according to the flight plan. The route may change prior to actual departure and while enroute, depending upon flight conditions and ATC changes.
The timezone abbreviation is dependent upon whether daylight savings time is or isn’t in effect (which itself is complex to determine, due to changing legal policies in different areas). It’s best to simply use an API that supports the tz_data/zoneinfo standard and convert the epoch timestamps into the localtime of that airport (and compute the current timezone identifier).