What does "noch stets" mean? and is it the same as "immer noch"?
Der Adler hat noch stets seine Zeit verschwendet, wenn er vom Raben lernen wollte.
This is a somewhat old-fashioned construction.
noch translates to still or yet and stets is a somewhat old-fashioned (but still in use) form of saying always or ever.
noch immer or noch stets is signalising that the speaker is anticipating dissent on their claim. The sentence could be translated as follows into English:
Yet, the eagle has always wasted its time when wanting to learn from the raven.
This is not a perfect translation, since the starting yet seems a bit unmotivated, since there is nothing it refers to. In the German construction noch stets or noch immer, this is suggesting that the speaker anticipates dissent, and still believes their claim to be true.