What you classify as your second "error" was one, BUT it is more than cancelled out by asking the tower for clarification. Good job. Treat ATC as a collaborator.
And that goes for non-towered airports, as well. Admittedly some of these are airports can be cells of anarchy (AWO has this reputation at times). But mostly what I encounter these days is a sort of ATC-by-committee. Letting other guys know you have them in sight, letting them know your intentions (I'll follow you, etc.), and it's downright collegial. My new home airport (Prineville, OR) works well this way.
Keep this in mind: Flight Instructors are not God. They make mistakes and you should question if something seems off. The same is true for that much more "experienced" pilot you may come to fly with. Instructors and other pilots will also bestow unsolicited wisdom about aviation that will mostly be true.