A person who habitually gives unsolicited advice is often called a (or Mister) Know-it-all (or Know-all). It's often understood that such a person's advice is either or both unwanted and inappropriate/unusable.
I don't think there's any particularly common expression for the advice/opinion beyond obvious forms involving preceding one of those words with unsolicited, unwanted, etc.
An extremely common (and quite rude) response to being on the receiving end is...
"When I want your advice I'll ask for it!"
...for which the typical British understated version is...
"I'll bear that in mind."
(which isn't always said dismissively/sarcastically, obviously).