1. No. PsE 11 is way out of date and will not run on certain newer operating systems.
2. If you mean the notifications for replies to a post or a reply you made on these forum there is no option for a Mobile, Text, notification. You can set up the mobile, Android/iOS email client to get your emails on your phone.
3. What do YOU mean by "What Do Plans mean"??? Are you asking about Subscription plans or Supprt plans?