Tutorial on Customizing Model

This link is a tutorial and it was in Dynamics 365 version, does anyone can give a link, book or tutorial that is developed using Dynamics AX 2012. Thank you in advance.

That way things are done in D365 and AX 2012 are different. AX 2012 has layers and models.
You can do customizations in the layer(and related models) that you have access to.

Do you have any link that I can refer to?