Hello Malaysia,
Thank you for reaching out, this is a great question. If you are wanting to be credentialed in more than one age group, the courses are birth-5 so they cover I/T, PK, and FCC. You do not need to take additional courses or re-take anything to get more than one CDA, you will just need both books. You will also need to apply for more than one credential to cover the age groups. So, portfolios for both age groups, separate applications for both age groups, separate verification visits, separate exams, etc.
And as far as your employment, you can still finish your CDA with us.
I hope that makes sense and please don't hesitate to reach out if you have any further questions!