I have following questions
1. How to find questions with patterns
2. In my profile, both tags, patterns, and design-patterns are displayed. Why both are displayed (and not the main one)?
That is how the system is supposed to work.
They are made synonyms because it's agreed that A means the exact same thing as B.
If they decided to keep only A and threw away B, then anything that would have been tagged B would be tagged A.
The end result being, you would still see the exact same subset of questions. The only thing that has changed is that you know about it.