Answer 1

Unown and history of the ruins. When the researchers make discoveries
the player will make note of them in the report. After capturing the
twenty-six alphabetical Unown forms, opening the hidden rooms in each
of the four stone panel chambers, and completing Page 7 of the Unown
Report, the '!' and '?' forms start to appear in the entrance hall of
the ruins. Catching these completes the research.

-Bulbapedia

Comments

You'll know the report is finished if the guy that usually gives you more Report notes no longer says "I'll let you know if I find out more."