I think it looks like an etiolated Echinopsis spachiana (Trichocereus spachianus).
They are quite easy to grow from cutting, lots of offsets/branching from the base). Lovely big flower

Looks like Neobuxbaumia polylopha.

Lots of animals (birds, insects, reptiles, mammals and etc.) eat flowers and flower buds. If snails/slugs, you can see them at night. Looks like also possible a small mammal. You might want to check it during night time. Sometime they can even hiding inside that particular pot/plant. Once I had mice...

It's an very old Matucana madisoniorum, the spineless form. That's about the maximum size.
Very thin fibrous root. It might lost some root during winter when it's dry.