Hi. Would you say that what is described by the use of a present perfect tense always include the present time?

Would you answer some more questions?

1. I think we can both use the past and present tenses and it would mean basically the same (but I am sure), although the use of the past tense may put the time of knowing in the past.

He has done the best that he knew/know how.

I think it can be said the following follows a similar line of reasoning as above.

He has done the best that was/is in him.

2. Can we write like this? If you have guessed what I was trying to say, could you write it better?

He has used it about six times during/for the past five years and he used it about seven times during/for the five years previous to that and he had used it about eight times during/for the five years preceding the period just mentioned.

3. What is the difference? Why would a person use a past tense in one and a present perfect  tense in another in a sentence when both are followed by a present perfect passive tense? I think both are grammatically correct though.

1.He did what has been told.

2.He has done what has been told.