Learn Russian: Вам не надо мне подсказывать.

They are triggered by different parts of the sentence. Вам is the logical subject of надо, because to say 'you need' in Russian, we literally say 'to you it is necessary'. Meanwhile, мне is the object of the verb подсказывать, which requires its target to be in the Dative case.

Why does подсказывать take the Dative case here?

In Russian, verbs that express helping, advising, or assisting often require the person receiving the help to be in the Dative case, without any prepositions. So 'to prompt me' translates as подсказывать мне (literally 'to give a hint to me').

Why is the imperfective verb подсказывать used here instead of the perfective подсказать?

After the negative phrase не надо (it is not necessary / there is no need), Russian almost always uses the imperfective aspect. This is a standard rule when telling someone that an action is unnecessary or gently telling them not to do it.

What is the exact nuance of the verb подсказывать?

It means to give someone a hint, whisper the right answer to them (like in a classroom test), or prompt an actor who forgot their lines. You can think of it as a combination of под (under/secretly) and сказать (to say).