How often should I check the operator each year?

The operator is be ckeched at least twice a year, including its rail and roller clearing.

The motor for the door acceleration can only operate one way: just opening, but no closing movement. When I turn the direction button to the left, it is completely different, as it does not open but just closes. Why is that?

Door Direction: since you have bought a bi-parting door, you may turn the switch for the so-called "Opening Direction" to the right hand side, then press TEST in order to see if it functions properly.

How is the access control to be connected to the GRIZZLY controller? Where is the signal connection between the access control (card reader) and the terminal unit? Is there any connectivity bushing on in the terminal unit?

1.The power of the access control (the control unit that is to be installed) must be at AC 24V or DC24-36V.
2.The detector of your access control must be switched to "Normally Open Detector without Voltage".
3.Connect the first two wires on the access control to the AC24V or DC24-36V power bushing (GRIZZLY terminal unit), and the other two wires should be connected with the bushings for "Normally Open Detector" on the access control.

How long is average life cycle of your products?

Its life cylce is at least at 2 million door movements -equivalent to more or less 7 years.

The outer sensors activates even if there is no object detected in its sensor beam, so the doors open without any reason. When I replace the said sensor nothing changes. Why is that?

You must first  remove all the sensor wires from the controller and press TEST to see whether the controller functions well without a sensor attached. If that is the case, it means that the sensor is improperly installed and you might have to reinstall it using the Installation Manual.