the examiner will see it. Around every page there are little borders and if you go past the borders then you're in trouble but as long as your answers are clearly crossed out and it is clear which answer is for which question then i absolutely promise you you'll be fine
Yes of course they will see it and mark it. Usually in an exam, if you write outside the standard box it has a note which says 'Do not write outside the box as it will not be scanned for marking'. If you write underneath the lines-there is no problem at all. Your answer will definetly be marked, Dont worry!