Actually none of your options. First lets consider your options:
Your first option: In this case people encounter with an unexpected
interrupt. People expect a bigger change when they click on a "Quit"
or "Validate" button.
Your second option: You should keep in mind that you want user participation, that cannot be acquired by force. For sure you don't
want a lot of "blah, blah, blah" comments, which users will writ to
escape the restriction. And of course there is a home button on
phones that terminate your app's workflow.
And finally your third option: It's ambiguous for user that distinguish what is the problem. It's better to give a better guide to him about the current situation. And again don't forget there is a home button on phones that terminate your app's workflow.
For making a better solution, we should have good understanding about the overall workflow.
You display a screen filled with some information >>> user read this information >>> User see the bottom buttons and find-out he should make a decision: validation or simply quit >>> he make decision and click on the chosen button >>> now after he has made his decision and has chosen the button, we go to next level by displaying a new activity and ask him to write an comment.
There are some important notes:
- Making decision and expressing comment, are two separate works that should be down on separate activities. compacting them on one activity only increase the complexity.
- We ask the comment after he has chooses the button, not before it.
- More activities with fluent flow is better than less activities with hurdles.
After all it's very very very important principle that say moving from left to right is indicator of progress (based on an Cleveland State University study). So your activities transition in this case should be right to left slide, to make a left to right movement sense.
- Left to right from top to bottom: easy down
- Left to right from bottom to top: easy up
- Right to left from top to bottom: hard down
- Right to left from bottom to top: hard up