How does stealing a tech boost work?

When a spy is sent on a "Steal Tech Boost" mission, what exactly does it mean to steal a tech boost?

1. Requirements: Does the other civ need to have the boost for a technology, but have it not researched completely yet? Or does the other civ need to have the technology researched already?

2. Effects: If the boost gets stolen, do you simply get it, or will the other civ lose it in addition? What if it has already researched the technology? Will the other civ lose the technology again if it gets stolen? What happens to other technologies that depend on the stolen one?

Based on my own game experience (getting boosts stolen by enemy spies), the answers to my questions are:

1. In order to steal the boost for technology T, the victim needs to

   • either have researched T already,

   • or have the boost for T.

   It is not relevant what the victim is currently researching.

2. Stealing a boost has no effect on the victim.