I opened my vs2010 solution with vs2012 but it didn't make any conversion as from 2008 to 2010 was happening. So my solution still remains the same as 10 label on it. when I make a new solution of course it has 11 label on it. I haven't got any problem running like that but I am curious. Is there any difference? if yes, how to convert into vs2012 solution?
There are some exceptions, but mostly you'll be able to open the same project and solution files files in both VS2012 and VS2010 SP1.
VS2012 may convert projects when you first open them, but the changes are (except noted in the document linked) backward compatible with VS2010 (ie using conditionals where needed to only apply to either version when loaded) Most project types will be left entirely untouched though.