which pokemon?

I do not all the Pokemon, that have the move, or learn the move Sheer Cold, but I do know that Kyogre should have it at level 70 when you catch him. Yes that is right, you get the Pokeradar after you beat everyone in the Elite four, AND see all 150 Pokemon in Sinnoh, which will grant you both the Pokeradar, and the National Pokedex. You are welcome.

1. Alright, well I had to do some research to answer this question, but nonetheless I have the answer for you, which was found on the SuperCheats pokedex (http://pokemon.supercheats.com/index.php). The Pokemon that learn Sheer Cold are: Dewgong, Lapras, Articuno, Glalie, Spheal, Sealeo, Walerin, Kygore, Snover, and Abomasnow, all found on this page: http://pokemon.supercheats.com/list.php?move=329

2. Unfortunately, yes, you must first beat the Elite Four and obtain the National Pokedex before you can obtain the Poke Radar. Luckily, you can obtain both the National Pokedex and Poke Radar simply by seeing all 150 Pokemon in the National Pokedex. Once you've done so, go in Rowan's lab in Sandgem Town and talk to him. This will trigger a series of chats and events that will have you obtain both the National Pokedex and Poke Radar.

The one`s that know it are Kyogre,Walerin,Dewgong,Lapras,Glalie,Spheal,Sealeo,and Abomasnow

I only know two that can learn sheercold kyogre (have to migrate from saphire) and articuno.
And not necisarrly becuse I belive (and ihave not tried this so don't be mad if it does not work) you can get a 150 guys by trading with a friend that has all the poke mon to fill up your pokedex and can get the natoinal and poke radar before you beat the elite four
hope this helped