"Geber" is an encoder/transducer (?). A device which transforms the an optical, mechanical or magnetical signal of a sensor into an electrical signal.
"Federgeber" sounds unreasonable, but I think it could mean "Weggeber für Federweg", which is in English "displacement sensor for spring deflection". I found corresponding examples in German and English (I won't insert them here).
Yes, may be.For example a pressure sensor in form of a spring.
I think a "Geber" is not an actuator, usually. But maybe there are exceptions.Maybe it's a coil spring actuator?