Always On Client connectivity

1. upgrade of every client connecting to 2012….? Do they need all to have .NET Framework installed.
2. After installing dlls for sql11 native client on system 2008R2. READONLY ROUTING NOT WORKING from those client where the native 11 client was installed from MS component package download. What might be the issue here?
3. On the Native ODBC client connectivity from 2008R2 servers do we have to use System DNS for the Linked server or just the readonly routing will connect?
4. why changing the URL ROUTING LIST get reset when trying to modify original settings.

Thanks

Suresh