I can make several sentences these given words and phrases, as follow, 1你最好别告诉他答案。You had better not to tell him the answer. 2告诉他答案？你最好别。Tell him the answer? I would suggest you not to. 3你告诉他答案？最好别。You tell him the answer? I would suggest you not to. 4别告诉他你最好(的)答案！Dont tell him your best answer! That's all i can think of at the moment. So you can tell only the first one is 100% correct (using given words and puncturation mark).

你最好别告诉他答案。 You'd better don't tell him answer. Of course you can tell him, but I hope you don't do that.

你最好别告诉他答案： 这是一个建议，当有人向你问一个问题的答案时，第三者向你提建议说最好不要告诉他答案。 你别告诉他最好的答案： 这也是一个建议。当你对一个问题有好几个答案时，第三者向你建议说不要告诉他最好的答案，也就是说其他的答案说了没关系。

The sentence '你最好别告诉他答案’ means 'You'd better not tell him the answer.' 你(You) 最好别(had better not) 告诉他答案(tell him the answer)。 别告诉他你最好(的)答案. In this sentence, you need insert a '的'. But if you say like this, it is a little weird. We often '别告诉他你的答案', as the answer often is unique.

you d better not tell him the answer. ---- 你最好别告诉他答案。 had better --- 最好；had better not --- 最好不要/最好别