To delete a track, right-click at the left, the Delete Track... 
Bring up the effect used for the circle, then click the white X to the right of its name to delete it.. .
To delete an effect on multiple clips, select them all on the timeline, click the effect icon on any clip, alter the clip back to its original state - in essence removing the effect.
Then click the green 'chain' button on the toolbar. Finally, click the white X. 
Each time you make a major change, Save Project File AS, giving it a unique # or name, so as not to overwrite prior saves. Using Save Project Files (no AS) will overwrite. From the HOME tab, the AS choice is available by clicking the caret to the right of the Save Project button on the toolbar. That way you're protected, and shouldn't lose anything.
You can also press <ctrl-Z> to go back, step-by-step. (Same as EDIT | UNDO.)