Hi Sankarsan,
You can follow any sequence to delete B1 and B2 clusters. It really doesn't matter which one you delete first.
Once you have deleted your B1 and B2 clusters, the system will understand that the time evaluation hasn't run for this employee at all.
After this change, please ensure that the time management status is 0 till 31.12.2014 and from 01.01.2015, it is maintained at 1.
Clear your IT0003 so that your next date for time evaluation is set at 01.01.2015.
You may not need to maintain earliest retro for time because time evaluation won't run prior to 01.01.2015 since time management status will be 0.
Thanks and regards,
Vivek