Play through only 1 Video Track

I’m on the cut page and I went through my videos and cut through the clips I like. I then created a 2nd video track and moved the clips from those tracks that I love and moved them to track 2. I then created a 3rd track and moved the clips I want to use in the final video, onto that track. This way I can change my mind later. How do I ONLY play the clips on track 3, one after the other?

You can't.

You can Disable the clips on V1 and 2 in order to see only the clips on V3, but you will have to play (or manually skip through) all the 'empty' space between those V3 clips.

There are other work flows that will get you there, however. You can Copy/Paste the clips you want into a new timeline, for example.

You can.

Non destructive: on the Color page, option click the tracks you don't want to review, enable Unmix, and you can then (in the Color page) play the clips on the remaining track(s) back to back, ignoring gaps.

Where there's a will, there's a way. ;)

Destructive: on the Edit page, Edit menu > Delete Gaps.