No, MCR is specific to the exact release. There is no chance of using MCR for R2012a with MATLAB R2010a .
Only MCR R2012a (and eventually later versions) can be downloaded. This is due to Mathworks license conditions.
For all previous releases, you must obtain your release-specific copy of MCR from the person (or organization) that build the stand-alone executable that you are using. No-one else can provide MCR to you (except Mathworks), not even if they happen to have it.
If you are the person who has the MATLAB Compiler license, then MCR is provided along with the MATLAB Compiler.
Note for reference: the version of MCR to use does not depend upon the MATLAB version you have, as executables built with MCR technology are not executing your licensed MATLAB version. The version of MCR to use is dependent on the version of the MATLAB Compiler that was used to build the stand-alone executable.
