To move subscribers who have a status of 'Held' back to 'Active', NTO should extract those subscribers using a tracking extract or a data extract activity in automation studio, then import those subscribers as
'Active' using an import activity or file transfer activity in automation studio or an import wizard in email studio. This process will overwrite their status in all subscribers list and allow them to receive emails again.
Contact Builder cannot mass update subscriber status in all subscribers list. Subscribers with a status of 'Held' cannot be re-enabled by contacting support unless there is a technical issue on Marketing Cloud's side that caused them to be held incorrectly. A SQL query cannot change subscriber status in all subscribers list directly. References: https://help.salesforce.com/articleView?id=sf.mc_es_held_status.htm&type=5
https://help.salesforce.com/articleView?id=sf.mc_es_import_subscribers.htm&type=5

To send a welcome email to contacts when a contact record is added as a campaign member to a 'Loyalty Member' campaign in Sales Cloud, Northern Trail Outfitters should create a journey with a Salesforce Data entry source and an email activity. A Salesforce Data entry source allows marketers to inject contacts into a journey based on changes or events in Sales Cloud objects, such as campaign members. An email activity allows marketers to send an email message to contacts in a journey. References: https://help.salesforce.com/s
/articleView?id=sf.mc_jb_salesforce_data_event.htm&type=5 https://help.salesforce.com/s/articleView?id=sf.
mc_jb_email.htm&type=5

The _ListSubscribers data view contains information about subscribers who belong to a specific list, including publication lists. It can be used to query subscribers based on their list ID, status, and date joined or unsubscribed. References: https://help.salesforce.com/s/articleView?id=sf.mc_as_data_view_listsubscribers.
htm&type=5

To separate subscriber opt-outs of the Enterprise and children's brands, Northern Trail Outfitters should select
"Subscribers will be unsubscribed from this business unity only" in Settings for each child business unit. This will allow subscribers to unsubscribe from one brand without affecting their subscription status for another brand. References: https://help.salesforce.com/s/articleView?id=sf.mc_co_business_unit_setup.htm&type=5

To limit subscriber records by BU based on the 'Region' profile attribute, Northern Trail Outfitters should select 'Define Subscriber Filter' for each BU on the BU Setup page and configure a condition to match the corresponding profile attribute. This will allow users who are assigned to a BU to only view and send to subscribers who have the same region value as their BU. References: https://help.salesforce.com/s
/articleView?id=sf.mc_co_business_unit_setup.htm&type=5