Add in "write in your own response" to a question slide

Hello,

My client is building a "mobile only" version of a course and they would like to have a slide that asks the learner to select form multiple options (choose multiple slide) but also have a "write in your own response" included among the options. Then they would like all the options the learner chose, along with the one they have written, to populate on a different slide.My questions are: 1. Is it possible to include a "text entry" option a "choose multiple" quiz slide, and 2. How would you create the feedback slide that would allow for any of the multiple options AND the "text entry" (if selected) populate on a new slide - particularly if you don't know how many options will be displayed.

One last thing - what aspect ratio to do you guys use if designing for mobile only portrait mode? I was using 405 x 720, but still getting a small dark bar at the very top when I preview it. 

Thanks!