Thank you, getting back to your original numbered list:
Currently, you have it set that all new registrants must purchase a product before registering but have no products available to these groups. There is a bug open internally to better check this prior to redirecting but it brings a better question on your site as you have no products available for these groups, why keep this enabled? To disable it, go to ACP -> Commerce -> Store -> Settings -> Purchase Settings -> disable "Force users to make a purchase when registering?"
No real response here but let us know if you have a question here.
This is due to your Group Promotion rule of moving Newbies to Members +. You can edit or delete this in ACP -> Members -> Group Promotions.