Hello,
In a scenario where I am retaking this Course, what is the process to complete Labs?
Current Scenario:
1) I noticed Labs I had completed previously are still considered earned certificates: Lab1a, Lab1b, Lab2a
Even so, I decided to debug Lab1a to check for any errors. Checkpoint error indicating steps were not complete. To bypass checkpoint error message, I went ahead and followed the instructions in Lab1a.
2) Challenges while working through my Lab1b
As I continue to Lab1b, I noticed duplicate records (data was managed) – confirming previously work are still saved. Screenshot example: List of Errors Found by Checkpoint shows discrepancy with inputs from Lab2a

Kindly, please let me know how I should continue working through course labs.
-RR
Yes, I see what you mean but you can't really rework the labs in the same account where they've already bee completed for exactly the reasons you're running into. The objects and data already exist so you can't add them again with the same name, etc. It just doesn't work. You would have to "undo" everything you already did first and then start again.
So at this point, either use the same certificates you had already generated, if your instructor allows. Or if they want you to work them again, then you'll want to get a new Salesforce account and go from there. At least, since you've already done them, it shouldn't take as long to do them this time.