[SDL] SDL + openGL support

[Guido Billi]

Hi, I am going to do some tests using SDL+OpenGL.
Now my questions are... in your experience, 

should I focus on OpenGL 2.1 or starting with a previous 
version of OpenGL?

Should I use older version of OpenGL because they are best 
supported or I can try to develope with newer versions?

I ask because I have found some codes that contains checks 
about OpenGL installed version and use older or newer 
features with a very simple approach like

  if (version < 1.1) do...
  else do...

Is this kind of check really necessary?

Thanks