Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. It may be confusing because sometimes, "experienced" is also used as an adjective (meaning expert) (link). Now, you might be thinking that "which one is the best" cannot be correct since it's a question format. "Which one is the best" is obviously a question format, so it makes sense that "which one the best is" should be the correct form.
Which is correct, "I like you the best" or "I like you best"? This is correct even if Mr. Smith is still working as a teacher, as long as the speaker's relationship to Mr. Smith has changed. "Ever" means "of all time", but the exact meaning changes with the tense.
Your original is correct as-is, except you need to remove the question mark at the end because it's not a question. My question is, what is the correct way to write this clause? I'm not sure if the two examples you have are grammatically incorrect, as such (I could see those sentences constructed like that - or at least understand what was meant). Which of them is correct? So, the version without the "the" carries both meanings (or sets of meanings). But "she walks most gracefully" could also be used to mean "she walks the most gracefully".
"She walks most gracefully" could be a synonym for "She walks very gracefully". Alternatively, it could mean that she walks more gracefully than she performs other activities - this is unusual, but would be clear from the context. "She walks most gracefully." v "She walks the most gracefully." However, "You're the best!" as a complete sentence can also be an expression of gratitude, meaning "You're awesome!" - whereas "You're best" rarely if ever has this meaning. If the statement was made in the context of a particular discussion (for example, about tennis), the two would have the same meaning (and the same range of meanings that we saw in the previous examples).
Find the answer to your question by asking. The adjective best is used in a copular construction with the dummy pronoun it. Here, we have the adjective best, but this adjective is attached to no noun. Because the noun car is modified by the superlative adjective best, and because this makes the noun car definite in this context, we use the.