1.) There seem to be 2 parameter sets available when passing info to the checkout – 3rd party (x_login) vs proprietary (sid). Is it ok to use either, or is there a particular one I should look to use?

2.) The knowledgebase indicates that information about the product must be passed (eg. c_prod parameter). Do these parameters have to match products setup in the 2CO account area, or can they be created on-the-fly from my app’s internal settings?

3.) If the parameter “x_Receipt_Link_URL” is set when sending the user to the checkout, is the user then redirected back to that url along with the notification data, or can I set the user to go to one page, and the data to go to another?

4.) I couldn’t seem to find much info on the INS feature that allows recurring billing notification, and so I’m unclear on how it differs from the normal callback procedure when setting up an integration, other than the user needing to opt-in to it from their account?

Many thanks in advance for your help!

Also, can anyone tell me if 2CO can pass back to the vB php file for username or does the reassignment of user from one group (priviledges) to another have to be done manually?

Sure would appreciate some pointers and thank everyone in advance for at least reading this plea.