I'm usually afraid to click on any unknown-to-me icons when working in Vegas, for this exact reason. Normally when I open Vegas, the timeline is at the bottom of the screen, the preview window is above the timeline, on the right side of the screen.

Just now, during editing, one of my happy finger hit something, the preview window became an elongated rectangle, AND showing 2 different video frames!. Normally, it's more like a square, showing 1 frame.

Please help me restore my sanity, I've been reading and trying to get back to how it was.

[1] How do I move the timeline to the bottom?
I already tried Options-Preferences-Display: select dock the timeline at the bottom, that was supposed to do the trick, but it didn't.
Edit: Figured out how to do it, just restore default.

[2] How do I make the preview window a square shape, instead of the elongated rectangle?
When I play the video, preview window behaves normally, showing only the video being played, in a squarish shpae. However, when I stop, the preview window reverts being an elongated shape, and showing another frame that's not in the video just played..
Edit: Still trying to solve this issue.

[3] Just under the top video track, there is a space (as if the video track is enlarged) labeled "B", how do I remove this space?
Edit: Figured out how, just restore default.

[4] Immediately above the "B", there's a stylized letter "X", how do I remove that?
Edit: Figured out how, just restore default

Thank you so much!!!
I'm using Vegas Pro 12.

Edit: As of this time, I still need help with [2]

Press numpad button "5" with selected any video event.

Just make sure you save your window layout in view windows layouts and you can go back instantly.