When does Sailor Chibimoon get her powers?

Answer 1

Depending on if you are talking about the anime or the manga, she gets her powers at a different time.

In the manga, she appeared in Act 23: Saisei NEVER ENDING, which is one of the final acts of the second arc (equivalent to Sailor Moon R). She transforms following the death of Sailor Pluto, when she cries over her friend and her tear transforms into the 30th Century Silver Crystal, similarly to how the 20th century Silver Crystal was revealed when Princess Serenity cried over Tuxedo Mask's fallen form in the first (Dark Kingdom) arc of the manga.

In the anime, she appeared in episode 103 (96 in the English dub), "The Arrival of the Tiny Pretty Senshi!" ("Hello, Sailor Mini Moon" in the dub), during the third season (Sailor Moon S).

By this point in the anime, the location of the lost 30th century Silver Crystal had already been revealed, but not its ability to be used as Chibiusa's transformation item, allowing her to become a Sailor Senshi. Instead, she returned shortly after the start of the Sailor Moon S arc, bearing a letter indicating that she was to be trained as a Sailor Senshi in the 20th century with the other Sailor Senshi. Unlike the manga, her powers in the anime were still in flux, and frequently didn't work as expected. Once she powered up in the SuperS season, her powers became more stable.