Canceling an amendment just removes the Form 1040-X. It does not undo the changes that you made. The only way to get it back to the way it was is to manually undo each change that you made.
If you use the CD/Download TurboTax software instead of TurboTax Online you have the ability to save a copy of your tax return file with a different name. Then you can make changes to the copy without taking a chance of affecting the original.
