Atul,

Please refer the below URL for ADSL2 and ADSL2+ router support;

http://www.cisco.com/en/US/products/ps5853/products_data_sheet0900aecd80394b7e.html

As far as XM and XJ release, X = A short lived, one-time release.An X followed by a sequential letter indicates short-lived releases. In the example, XA, XB, and XC, the X in the first position indicates a one-time (short-lived) release originating from the major Technology (T) train. The letters in the second position (A, B, C, D, and so on) are sequential letters used to differentiate the releases.

Please refer the below URL for details:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1818/products_tech_note09186a0080101cda.shtml

I hope it helps.

Regards,

Arul