I have a package that is developed in SSIS 2012 using Visual Studio 2010.
Is it possible to deploy/attach this package on SQL Server 2008
You cannot run it with the 2008 version of dtexec and you certainly cannot deploy it into the catalog, but if you could install the minimum you need to run SSIS 2012 onto a server somewhere you could then execute the package from filesystem with the 2012 version of dtexec.
See also http://msdn.microsoft.com/en-us/library/bb522577.aspx