Delete files / folders from tape backups

You will have to find ways to ensure that each client uses there own set of tapes, because tapes are serial access devices you cannot erase or overwrite  only part of a tape. Erase or overwrite operations are against a whole tape. Probably easiest way to set this up if you only have one media server and library is use slot partitioning to define ranges of tape slots in the library for each customer and the use individual jobs that go to the correct partitions

In theory, the disk backups can be individually deleted however as I noticed you have some old BE versions in your list, and we allowed an append to disk media in those versions, there is a small caveat covering where you may have appended customer A's data into the end of customer B's backup files because at the time the jobs were appending (Newer versions of Backup Exec do not allow this, and with older versions we did recommend starting disk based jobs as overwrite which woudl avoid it) Hopefully, however, your environment was setup with separate backup to disk locations per customer which would also avoid this issue against disk.

For existing data you will need to duplicate the data of all the customers that you need to still keep their backup sets before erasing the tapes (this is if you have a customer insisting you delete their data from shared tape.) Basically this will be a very time consuming process and you will have a lot of work to do to make sure retained customers can still restore their older data and to prove to a leaving customer that you no longer hold any of their data if the environment was not setup to ensure the separation of the data when you backed it up.