TIL: You need a comma before which and another one at the end of the nonrestrictive phrase; for example:
Jeff’s new car, which is less than a month old, already started leaking oil.
And I learned that we can omit "which is" or "which" in the following sentences.
This dog which/that is following us is very big.
This dog following us is very big.
This dog, which has 4 legs, is mine.
This dog having 4 legs is mine.
My question is: Do we need commas for the last sentence?
Since "having 4 legs" is a nonrestrictive phrase.
This dog, having 4 legs, is mine.