Attach Custom Information to Commerce Order Model
Add a custom plain text field to your orders, say test.

Then, when calling updateCart, you can add data in to this custom field using a form with an input named like this:

  &lt;input name="fields[test]" type="text"&gt; etc...


This data will then get saved with the order.  This same approach can basically be applied to any field/type.

To actually validate the data, you'll need to look to making a plugin, most likely listening to onBeforeSaveOrder to check the vailidity of the data.  If valid, great, if not, set perfomAction to false and return an error on the Order model.  

See https://craftcommerce.com/docs/events-reference#commerce_orders.onbeforesaveorder