How to Unmap a datastore from esxi host without loosing data

Dear team,

I want to unmap a datastore which is mapped on two cluster (cluster1 10 esxi host and cluster2  4 esxi hosts)

Query1

Which step will be correct

unmount => detach => start storage movement activity (poweroff storage) => move the storage => poweron => attach => mount

or

unmount => detach => san team will unmap => start storage movement activity (poweroff storage) => move the storage => poweron => san team will map the datastore =>attach => mount

Query2:

once i browse i am able to see vpshere ha and dvs data folder, just want to confirm if i want to unmount and detach the datastore will it allow me to do that or it will throw an error, please confirm.

Query3:

if we unmount and detach a datastore, before that do i need to unregister all VMs??

regards

Mr Vmware