which of these series has da most riders?

Kamen Rider Gaim - Ryuki: 13 / Hibiki: 17 / Gaim: 22 / Ex-Aid: 11

Which series has the greatest number of distinct transformation belts?

Kamen Rider Zero-One - Zero-One: 14 (Zero-One Driver, Zero-Two Driver, A.I.M.S. Shotriser, Metsuboujinrai Forceriser, Zaia Slashriser, Zetsumetsu Driver, Cycloneriser, Thousandriver, Ark Driver, Eden Driver, Shot Abaddoriser, Slash Abaddoriser, Metsuboujinrai Driver, & Zein Driver) / Hibiki: 0 / Saber: 5 (Seiken Swordriver, Jaken Calibur Driver, Haken Bladriver, Seiken Saikou Driver, & Doom's Driver Buckle) / Revice: 10 (Revice Driver, Two-Sidriver, Libera Driver, Demons Driver, Cyclotron Driver, Vail Driver, Week Endriver, Destream Driver, Chimera Driver, & Juuga Driver)

Which of these Riders comes from the farthest in the future?

Kamen Rider Kikai - Century (2071), Kikai (2121), Aqua (~2051), Ginga (2019)

which of these motifs has never been used for any official Rider or Rider form?

Cactus - Kamen Rider OOO Shigazeshi Combo (Cow), Kamen Rider Imperer (Gazelle), Kamen Rider Goda (Centipede), Kamen Rider Demons Anomalocaris Genomix (Anomalocaris)