Navitasan, for the sake of clarity, I had better take another look at at your questions.
With the first statement, which word is emphasized makes a difference in meaning. Example:A-"The blue car is fastest when you put super-fuel in it."
Meaning: It goes fastest at that time. I am comparing its perfomance at that time to its performance at other times.
and if I say:
B-"The blue car is the fastest when you put super-fuel in it."
I am comparing it with other cars and say if you pur super-fuel in it, it goes faster than all the other ones.
- The blue car is fastest when you put super-fuel in it.
That statement compares the blue car with other cars.
- The blue car is fastest when you put super fuel in it.
That statement compares the car with itself at different times.
Your interpretation is, in my opinion, the most likely meaning of the "bare" sentence (absent context or other cues).
The same goes for the second sentence. Your interpretation is the most likely one.
(Instead of faster than all the other ones you can simply say faster than all the others.)
Answer: Probably not, but they could.But may-be I could use A even when I am comparing the blue car with other cars?
Question: Do A and B mean the same thing?
To the first question, yes. To the second question, no.As for:
C-The blue car is best.
Question: Can I use C when I want to say the blue car is better than all the other ones? (Or only when I want to say: "Using/ Driving ....) the blue car is best.")