Back/Cancel Button on Registration/Checkout

1. Where should back button be placed?
2. Why is the cancel button used?
3. Where should back button be on app?

Where should back button be placed?

Place a persistent Back to Top button in the lower right side of the page. This is where people expect to see it. This position is out of the way, but noticeable. When the button is placed in a different place on the screen, it is often ignored.

Why is the cancel button used?

Cancel is mainly useful for multi-step dialogs where the user has progressed past one or more pages with actions. At this time, pressing the Back button will not undo these actions and it would be better if the user would click Cancel.

Where should back button be on app?

Since the top left is pretty standard for most apps, this makes it recognizable for the user and therefore easier to find and use. This position is only difficult to reach for mobile devices. That is why the bottom left would also be possible, but the most important option like a next button is at the bottom.