Who's that Cacti?!

[ChefRico]

Is anyone able to ID these cacti? Bought them from Kew Gardens last year and the pack they came in was not labelled. Grown particularly fond of the red haired one (Red Haired Irishman?) and the... dark green one that doesn't have any spikes and I wonder if it is even a kind of cactus at all...

Would also be curious to know if any of them will flower/bear fruit.

 

[Marck]

The cactus on the left is Mammillaria elongata, native to central Mexico. There are numerous forms of this attractive species with different colored spines. This cactus will flower and bear fruit, but not the type a human would want to eat.

The cactus in the center is a monstrose form of Cereus repandus, native to South America and the Caribbean, though there is some debate if it is that species, as this monstrose form rarely if ever flowers or bears fruit, which would help determine the exact species.

The plant on the right is not a cactus, but rather the fairy washboard (Haworthiopsis limifolia, formerly Haworthia limifolia), a succulent native to the Eastern Cape of South Africa. Haworthiopsis is related to Aloe, both being in the Asphodel family (Asphodelaceae).
Haworthiopsis also flower and bear fruit, but again, not the kind a human would want to eat.