Relationships between applications?

Relationships between applications?

I am using the free version and have created three applications - inventory, orders, and customers.  I have tried using lookup fields to automate the orders form (bringing in data from products and customers), but cannot seem to get access to more than the single field I choose in the lookup field.  Creating formula fields, or criteria in other types of fields, in the orders form does not see have a way to access other fields in the Products or Customer applications, except the single field chosen in the lookup.

Is this a pay feature, or am I going about this in the wrong way?  Should I create a single application with an order form, a product form and an inventory form?  Would that create a DB with three linked tables?

Thanks,
Dave