Is there any problem with installing a prehung inswing exterior door backwards as an outswing?
I don't recommend this if the door is exposed to any sort of weather.

The threshold is different. This is the big issue, as you don't want standing water, and an exterior door isn't designed to deal with indoor rain. You'd also end up with rain pooling on the top edge of the door, which might be bad. Make sure all the hinges are rated for outdoor use; you don't want them to rust, and that's something an inswing door doesn't need to deal with.

Code wise, if you're switching from inswing to outswing, make sure there's enough room near the front door. If you have steps up to a small front stoop, an outswing door may not be code compliant, as you'd need to step off the stoop to open it. (And would be generally annoying to deal with.)