Wth is Ultrakill and should I get it

So I keep seeing references to Ultrakill everywhere (especially in Roblox Pressure community) even though I have no idea what the game is even about. Can someone answer these questions:

  1. Is it good game
  2. What age rating should it be
  3. Should I get it
  4. Is Sebastian Solace there
  5. Will I go insane from playing it

Thanks!