All doors lock automatically when the lock side is pressed. They unlock when the unlock side is pressed.
Driver's door

Front passenger's door

To lock all the doors from an open front door, press the lock side of the door lock switch and then close the door.
NOTE
When locking the doors this way, be careful not to leave the key inside the vehicle.
Locking, Unlocking with Transmitter
Auto Lock/Unlock FunctionMazda 6 Owners Manual: Rear Cross Traffic Alert (RCTA) (Some models)
The Rear Cross Traffic Alert (RCTA) system is designed to assist the driver in
checking the area to the rear of the vehicle on both sides while the vehicle is
reversing by alerting the driver to the presence of vehicles approaching the rear
of the vehicle.
The Rear Cross Traffic Alert (RCTA) ...
Mazda 6 Owners Manual: To Resume Cruising Speed at More Than 25 km/h (16 mph)
If some other method besides the OFF/ CANCEL switch was used to cancel cruising
speed (such as applying the brake pedal) and the system is still activated, the
most recent set speed will automatically resume when the RESUME/
switch is pressed.
If vehicle speed is below 25 km/h (16 mph), incre ...