1. Set the screen size so that back button is not visible at all.
2. Use enableTokenValidation in the application.
2nd solution deserves some attention and more details. Basically when you enable token validation for a page, that page is annonated with the current object for all the iterators used to render that page. This annonation is then submitted to the server along with any data. At that point the current object of the iterator is compared with the annotation. If they differs and exception is thrown. So, this way user can be prevented to see weired behavior.
To enable just go to page definition file and set the tokenValidation property to true.