Hi Mihir,
If you only have the scenario that some users may not use released products, then you can indeed use the field level security. This can be done by a customization, but also configuration on the Security configuration form. However, you will need to have two different roles. One role which will block the Item field and one role which does not have this restriction.
When you have more scenarios, like one user to have both roles or restriction on the category field (or values), please specify all scenarios as the field security might have some downsides.
Also note that XDS is also available and recommended above RLS for AX 2012. RLS is available in AX2012, but deprecated for future versions.
