If a question is related to automation and it mentions that a file will be available in the FTP always at a specific time, your answer will be an option with a scheduled automation. Scheduled automations are used when you know the time a file is pushed into FTP and it always runs at a scheduled time. If a question is related to automation and there is an uncertainty when the file will be pushed to FTP (ex; a day before last working day / if a date falls on a weekend, it will be available on last Friday etc.), your answer will be an option with a Triggered Automation. Triggered Automations are fired as soon as a file hits a specific location within FTP. Transfer activity is involved when file in encrypted.

Explanation
To target all customers who have registered to receive push notifications, Northern Trail Outfitters can use two ways to create this segment:
Using Mobile Studio, create a Mobile Push Filtered List then filter on the MobilePush Demographics attribute group. This is a user-friendly tool that allows marketers to segment their mobile push audience based on criteria and conditions without coding.
Using Automation Studio, query the _MobilePushDemographics Data View and save this to a data extension. This is a more advanced tool that allows marketers to segment their mobile push audience using SQL queries and data views.
Using Journey Builder or Contact Builder are not ways to create segments for mobile push audiences, as they are used for different purposes. References:
https://help.salesforce.com/s/articleView?id=sf.mc_moc_create_a_filtered_list.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.mc_as_query_activity.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.mc_as_data_view_mobilepushdemographics.htm&type=5

Explanation
To unify the messaging and branding of communications while still allowing personalization and timing of campaigns, Northern Trail Outfitters and its subsidiaries should use Distributed Marketing. Distributed Marketing is a tool that allows marketers to create consistent and compliant messages in Marketing Cloud and distribute them to Sales Cloud or Service Cloud users for sending. Distributed Marketing allows Sales Cloud or Service Cloud users to personalize and schedule messages based on their customer interactions and preferences. References:
https://help.salesforce.com/s/articleView?id=sf.mc_dm_distributed_marketing.htm&type=5

To report on 'Not Sent' contacts in Journey Builder, Northern Trail Outfitters should use the standard report
'Subscribers Not Sent to'. This report shows how many contacts were not sent an email due to various reasons, such as unsubscribes, bounces, duplicates, or errors.References:https://help.salesforce.com/s/articleView?id=sf.mc_rn_subscribers_not_sent_to_report.htm&ty