Volvo V70 Forum : “how can one get emergency access to gas cap”

I guess your fuel door lever has stopped working?  If so, you can gently pry with a flathead screwdriver, thin-bladed knife, etc., to release the door.  Be careful so as not to cause damage to the latching mechanism.

their is also a pull handle in trunk on upper left.

Open the trunk of the sedan. On the fuel door side in the trunk, find a large plastic knob that holds a lining door/cover. Turn it to loosen the lining door. Open the lining door. You'll see the connecting rods and mechanism that operate the fuel door lock. Disconnect the rod. The fuel door can now be open easily. No more lock on the fuel door.
If your electrical controlled fuel door lock system does not work properly, you can simply disconnect the mechanism.
For a temporary stuck lock, instead of the above total disconnect, you can pull a handle on the mechanism to unlock the fuel door. Volvo thoughtfully add the handle to the mechanism.