No. You can see nothing in complete darkness
Nothing can see in complete darkness.
No, you need a subject. For example, "I went to see Mike" and "He went to see Mike" are complete sentences.
You have to have caught all of the Pokemon (not just see them) to complete the Pokedex to show to Gamefreak, or have it during a trade
You have to see them
Yes , see related link below .
You don't have to see Heatran in order to complete it.
did not see
I believe that there are a few puzzles you have to complete. When you complete them, you will drop down, and see the Unknown.
See related links for a walkthrough.
see the related link
you can't