Understand that you are currently in the user research phase, just like to point out that the way users respond via audio only and video (with or without audio) are very different.
And typically people’s attention span on receiving answers via audio or video are less than 5 seconds because audio and visual cues work based on short term memory usage of users.
Start with a button that says Record Answer
when clicked on Opens up the front camera by default (General Camera UI would Do)
It should also have the option to trigger back camera
once you hit the shutter it starts recording
You Hit the shutter button to stop
after stopping the recording on the right side of the shutter there will be TICK icon
and on Left ...