@Ravi_Peddhibhotla If you are on the desktop version, pulling from the github masters, should get you the latest version. Build 20 does seem to be the latest version.
To answer your question from the original post,
1. No it does not require pairing code per skill
2. It should only have to be paired once.
There is an identity folder that was created when Mycroft first ran. You can find it in the ~/.mycroft/identity/ directory. If that file exist then it should need to repair.