Is it possible after makeing 20 Pages A-Parent could I change 2 or 3 pages in A-Master to say something else different than the other A-Parent Pages? Do I have to make a B-Parent for those 2 pages that I want something differet on it?
You can rename any of your master/parent pages with any label you'd like. Examples:
I recommend keeping the A, B, C prefixes because they are very helpful when "A" appears on the thumbnails in the pages panel. You can quickly see which master/parent is applied to each thumbnail. So my examples become:
B- Opening page
E- Order page
To change the names, right-click on each one and select Master/Parent Options. Write whatever you want in the Name field.
You can Ctrl (Cmd) + Shift click on a Parent (or old name Master) page object to override it onto the current document page and then edit it. If you waant more than one page to have the same new text, make a new Parent page based on A, then overide the object there and edit, then apply the new Parent where you need it.