The agreement encompasses all three tier levels. Whatever the rules are for certificate use on AC, the same will apply when using them on CP...and vice-versa. I'm not at all familiar with CP's stickers (give a few days though!), but I imagine the restrictions are similar.
The 'standby at gate only' is mainly due to some computer problems they have to work out between RESIII and Sabre.
Last but not least, the reason behind the sudden change: customer feedback and requests. It was also inevitable!
Have fun!
Emp