1. Labels and exclusion reasons will only be visible to others if the blind mode is off.
2. You can easily remove your own labels/reasons. You simply select the reference and then click on the "Reason" (or label) box. There, you just click on the label you want to be cleared and it will be cleared. Notice the "-" in front of it. Note that you can only remove your own labels or exclusion reasons. However, once you make a decision on an article, you can only switch to another decision.
3. You add the one record the same way you uploaded your first search. Just put in a file and click on "Add" in the search box on the left panel in the review view.