The town of Wolfville boasts spectacular tidal flats, an annual apple-blossom festival, and the beautiful campus of Acadia University.
Explanation:
You need a comma after "flats" to end this element in the series. The comma after "festival" is optional. You should not use a comma after "campus" because the phrase that follows is restrictive.

The university gave the two top scholars, Janet and him, gold medals and framed certificates of merit.
Explanation:
The comma after "gave" in the original sentence incorrectly separates the verb from its object. You need a pair of commas around "Janet and him," because the element is non-restrictive.

Everyone with tickets to the seven o'clock showing of the Rolling Stones movie should move to the front of the line.
Explanation:
There should be no comma after "everyone" because what follows is restrictive information. Do not keep the comma between "movie" and "should"; doing so incorrectly separates the subject from the verb.

Stacey, who was usually quite decisive, faced a true dilemma in her last year of university.
Explanation:
You should use commas around the non-restrictive clause "who was usually quite decisive."

The ring on his finger is solid gold.
Explanation:
The phrase "on his finger" is restrictive, so you should not set it off with commas.