Which is it?

I'm seeing alot of advice here given out that 5 or even 6 weeks is conclusive. This is very confusing because some of the people are not even stating the generation of test they have taken.

The 3/4 generation tests are the ones for the 6 week area, if someone had a 1/2 generation or we don't know which they had why are they still being told they are good to go?

I don't know the difference in all the tests but if someone could explain that, that would be great.

I understand the 4th gen. is good for early detection due to the P24, however, the others don't use that.