Sorry for late reply !!
So they checked the passport online and also CJ had the application file of my Dad with her while interviewing my dad on video call .
She had all the info about my Dad. Even she was able to clarify about entry/exit of my Dad without asking my Dad.
No you don't need to prepare for test again but definitely you need knowledge about the city/province your are living in. In my Dad's case , CJ had never been to Saskatchewan so she kept asking to my Dad about weather/culture/population other things about SASK.
Just be honest about your application ( whatever mistake you made ) and be polite/humble. Seems like CJ know about all mistake and every details of your application .
THEY ARE EXPERT AND THEY LOOK IN TO APPLICATION VERY DEEPLY !!
GOOD LUCK TO YOU !!
And one more thing guys !! his ecas was changed to decesion made and now other line has been added in his ecas to attend the oath ceremony !! They have sent a letter in mail and that will be official letter for his oath !!!!
Cheers !!!