Merge the user accounts in M365

Question

Hello Folks,

Need your suggestions on the below query !!

Customer has an AD domain ( CORP ) and they are separating from the company with new domain ( ABC )

Currently they have M365, SharePoint and Teams access, As they are separating from the CORP domain they want to have a separate tenant with M365,Sharepoint and teams and still they will be login to CORP for internal resources access

• We will create a new tenant and enable the access of M365, SharePoint and Teams access to the ABC domain users
o COPR domain will not allow AD connect tool to sync ABC users to new tenant
o Manually we will create the users in the tenant and allow them to use M365,Sharepoint and teams
o User mailboxes are linked mailboxes
o ABC users are ok to use two credentials for accessing the resources internally and externally

• Once the ABC users are disconnected from CORP can we move and merge these users to the ABC tenant
• If we are syncing the users from ABC via AD connect tool to the ABC tenant ( Will the same user objects merge in the Tenant )
• In case we have to delete the users in the M365 tenant what happens to the user data of M365,Sharepoint and teams
• Can we merge the ABC users in the cloud with On prem AD with AD connect tool.
• Can we remap the users data if we delete them in the cloud and sync them again with AD connect