If your door is a manual door and doesn't have a motorised opener, then yes: you can very easily open the door from the inside and the outside. If the door is locked, however, and you're on the outside of it, you're going to have some trouble opening it.
Unless you have built-in precautions against this, you can straighten out a wire hanger and insert it through the top of the garage door. Feel around until you reach the emergency latch. If you can hook the cord, slowly pull on it. Once the safety release is disengaged, you can roll the door up manually.
To open a garage door from the outside, use the emergency release key to open the emergency release lock. Then, pull the cord down to unlock the door. Use the same key to unlock the manual lock (near the center of the garage door), then turn the handle vertical. Finally, lift the door up from the bottom to open it up.
Almost all garage doors feature a manual release function to bypass the opening mechanism during power outages or in case the motor malfunctions or a garage door remote breaks. To trigger the manual release, locate the short rope hanging down from the garage door track. It usually ends with a red, T-shaped handle.
Press and Hold the Garage Door Button
Although a temporary solution, but to bypass safety sensors on the garage door, you can press and hold the button to fit on the garage wall. The doors start going down. Release the button when it is completely closed.
Lifting the door manually is not recommended but it is possible. If you decide to open the door manually use extreme caution garage doors are heavy and they feel heavier without working springs. When possible have another person assist in lifting the door.
Many electronic garage doors come with a bypass switch, allowing you to override the system and manually lift it open when needed. To locate the bypass switch, look for a red rope hanging down from your garage mechanisms. This emergency release cord will be attached to the trolley in the center of the garage door.
You can disable the garage door opener by pressing the Smart Button on your motor for several seconds to void all the remotes connected to your home. It's vital to deprogram your garage door opener and disconnect all programmed devices.
If the problematic cable has caused your door to become stuck in an open position, you should call emergency garage door repair technicians and stay there until they arrive. If this isn't possible, and you can't leave your home exposed, you'll have to cut the remaining cable to close the door.