Can only the Moon Princess can use Moon Spiral Heart Attack since the Moon Kingdom is shown while Sailor Moon uses that attack?

Answer 1

Presumably so, yes. Each of the Sailor Senshi's attacks are individualized to their planets and elements of influence. Even when Sailor Venus disguises herself as Sailor Moon in episode 102 "A Pure Heart Stolen! Usagi's Biggest Crisis" (episode 95, "Birthday Blues, Part 2" in the dub), she uses a variation of her own Love-Me Chain Attack, called "Hissatsu Love-Me Moon Chain," ("Hissatsu" translating to "Sure-Kill").

The only attacks that multiple Sailor Senshi have used is the non-powered attack "Akuryo Taisan" (used in conjunction with an ofuda scroll to dispel demons; both Rei/Sailor Mars and Sailor Venus have used this attack) and the few attacks that both Sailor Moon and Sailor Chibi-Moon (Mini-Moon) have in common, such as "Moon Gorgeous Meditation."

Because Chibi-Moon seemed to have many of the same transformations and attacks as her future mother, it stands to reason that she might someday also inherit some of the attacks that we never saw her use, such as Moon Spiral Heart Attack, as she too, is the heir of the Moon Kingdom.