The first Mock Exam for the LFCS seems to have a bug due to the fact that question 13 overwrites what you need to do in question 6.
In question 6 you handle partitions under /dev/vdb and then question 13 comes and formats your /dev/vdb and as such the 3 partitions that are created for the first questions no longer exist.
As such when you end the lab and are evaluated it will see you fail question 6 due to no longer having vd2 and vd3.