Different levels of technological development

[Or Entity?]

Take a look at these three scenarios:

2 We do not know how to build a fusion reactor.
2. We know how to build a fusion reactor, but we haven’t built one yet.
3. We have built a fusion reactor.

Does the three alternatives describe different stages of technological development?
Or is two of them equivalent?
If Yes, which two?

 

[Astronuc]

1 We do not know how to build a fusion reactor.
2. We know how to build a fusion reactor, but we haven’t built one yet.
3. We have built a fusion reactor.

These represent 3 distinct levels of technological capability.

1. Lack of capability or fundamental knowledge, with respect to controlled fusion. One can have basic knowledge of fusion from expriements, from the development of thermonuclear weapon, and observation of stars.

2. Knowledge of the basic science and technology, but it's more like, we think we know. Until it's actually done, then the knowledge is not proven.

3. Experience. One actually proves the knowledge and capability.