Butterfly is a vertebrate

No, they have no bones (neither does a shark - but it is a vertebrate). It lacks a back-bone (the equivalent is in front or below). A butterfly is an insect and most insects are classified as invertebrates. Butterflies have an exoskeleton, which is the outer covering of an insect.
No, butterflies are invertebrates.
No - butterflies have a soft body with no bones.