Here are the answers to your questions:
- Unfortunately, you cannot see the unsubscribe reason on the subscriber record. You can either see it on the collective list of All Subscribers:
Or you need to run an SQL query against the _BusinessUnitUnsubscribes data view to be able to see it. Here is an example query:
SELECT
SubscriberKey,
UnsubDateUTC,
UnsubReason
FROM _BusinessUnitUnsubscribes
No idea why that would happen - this is very odd and I'd create a support case and ask Salesforce support to investigate it.
Depends on what information you are trying to get. Some basic data cen be gathered from the _ListSubscribers data view, but if you want the custom attributes, you will have to join it with the _EnterpriseAttribute data view. Here's a basic query, in which you'd have to replace the list id with the id of your All Subscribers list:
SELECT
EmailAddress,
SubscriberKey
FROM ent._ListSubscribers
WHERE ListID = 123