Yes, by using a text field to add a custom URL.
Yes, that is possible.
Yes, it is possible. You can find the “max” field available in each add-on.
Yes, it is possible. You will need to copy the following tabs: yith_wapo_groups and yith_wapo_types.
Yes, the add-on contents are shown in the order and, as a consequence, in the order email as well.
No, our Product Add-Ons plugin does not work with REST API.