I can actually answer most of these!
1. A figurative ascent is totally okay as long as the literal ascent is somewhere in the game at some point. You can put the ascent at the very end of your game if you want, and have multiple ascents, figurative ascents, or anything in between. The main important thing is that the literal ascent is present in all playthroughs of the game (so it can't be optional or postgame content)
2. We can submit as many entries as we'd like!
3. I'll let Human answer that one but from what I recall, there's no lower limit to playtime (5 minutes is a suggestion because it's difficult to have anything substantial under that amount)
4. I'll also leave this one to Human's discretion but I think as long as the player will see this ascent during their playthrough (which means including during or after the credits), it should be okay
5. The player does not need to be controllable during the ascent, but I think 'the player must go there' means that all players must see the ascent in some form.
If I got any of these wrong, Human can correct me!