One theme I have been wondering about...realistically, do Earthlings have a chance at reverse engineering alien technology?
I know that during World War II there were efforts to reverse engineer captured equipment.  But the opponents were fairly close to each other in their level of technology.
		
		
	 
I was reviewing an old thread, 
How Difficult Is It To Reverse Engineer Technology?
This is a second theme in reverse engineering-not being able to simply copy a machine, but producing something similar in function at your own tech level.....
Quoting Saturn0660:
"It also depends on your tech level...You might be able to come up with something close ...I'll point out the Tu-144.  A copy of the Concord thought to have come from stolen blueprints.  Some have also thought that the  Buran was mush the same way.  Not so much reversed but copied/built at their tech level...."
Quoting Manti:
"One thing that was reverse engineered...  The B-29 bomber was completely replicated as the Tu-4 Bull bomber...there were significant differences, and some of the fire control radar systems on the B-29 were deemed too complex for exact duplication, but other systems were substituted that did much the same thing...Granted, the B-29 was simply 1 generation ahead of Russian airframe technology so the scientific concepts weren't too far ahead...but even then there severe problems...."
I understand that EA pulse cannons were derived from captured Dilgar weapons.  I suspect that the Narns' big laser cannon (which damaged a Shadow ship) was derived from an old Centauri weapon.
The limits of this kind of reverse engineering are probably defined by the bleeding edge of your fabrication techniques.
A third version of reverse engineering would be just within the limits of what is possible for you.  Not being able to make a duplicate or a derivative, but still being able to make something useful.  The EA came across an alien shield system, but initially could make work only the simplest application, the Interceptors.  An interceptor was a device that fired a bolt to disrupt/neutralize enemy weapons fire.  Eventually, the energy-web was derived from interceptor technology, a sort of proto-shield that diffused enemy fire so it hit the hull less hard. 
Interceptors/e-web became almost an alternative tech-line.