Mass Update Line Manager via HDL Inquiry

Summary:

I would like to complete a mass change to update employees line manager. I have been reviewing KB18709 as it does provide HDL information.

For the HDL, is there an available SQL that can be used to extract the necessary data for the HDL?

Is there more information that can be provided about the process that may be beneficial in its set-up and execution?

Once the HDL is complete, will this add a Change Manager record to each team member's employment history section in employment info?

Is there a maximum number of employees that can be updated at one time?