The movie was either from the 1960s or 1970s. I watched it on regular TV in the mid 1970s. The waterfall seen is in the end where a couple drink from the waterfall and begin to age from young adults to seniors.
The movie was a fairytale/sci-fi movie about a young man who meets an old man on a hill with a spinning wheel who sends him on a quest through a mountain passage. A huge boulder is ready to fall to block the passage but the man gets through and achieves his first test.
Second test: he gives a talking flower a drink who then turns into a princess, then he rescues a bird from a cage who them turns into another princess. Then, he is captured and tied to a tree and uses a magic leaf to hum a tune that frees his ropes.
He finally completes all the tests and can marry his princess. When they are outside the castle he runs to the waterfall and drinks the water which ages him and she decides to drink it as well.