Question

what is the key difference between regeneration and fregmentation

Answer 1

Regeneration is development of a new organism from the parts of parent organism.Eg planaria.
Fragmentation is the development of a new organism by the division of fragment by fragment or part by part.Eg spirogyra

Answer 2

In fragmentation the organism gets matured and breaks up on its own.

But in regeneration the organism has to be cut by force in order to reproduce

Hope it helps:)