Questions about example sentences with, and the definition and usage of "Squidgy"

The word "squidgy" is not used in the US. It means soft and easily squashed. "Squidgy round the edges" means soft and flabby (fat).

That word is very uncommon, so you don't hear it used that often

In this phrase, "edges" is just the outline of the person's body. "Edge" means the outside limit of something, the border of something, so here it means the outside of the person's body. "Squishy around the edges" = a bit chubby (having a bit of fat on the outside of their body)