Probably should distinguish for OP the difference between "hard product" and "soft product" Polaris.

"Hard product" Polaris is the lie-flat pod seating used on many United widebody planes (787, 777, and 767). These planes fly predominantly international routes, but sometimes are used on domestic routes as well (especially if they can squeeze in a flight between international flights - for example, I took a flight recently DEN-IAD on a Polaris 777 that was headed to Frankfurt next). When on a domestic route, it's marketed as "United First" even though it's the same Polaris seat.

"Soft product" Polaris is the international (except North/Central Am) business class service, which comes with lounge access, nice bedding, (mildly) upgraded food, wine, liquor, etc. None of these things come on domestic flights when the plane has Polaris seats (except free liquor, and wine that is lower quality than international; and food, which you would not get at all in economy).