How should an Architect automatically redirect users to the login page of the external Identity provider when using an SP-Initiated SAML flow with Salesforce as a Service Provider?

A client is planning to rollout multi-factor authentication (MFA) to its internal employees and wants to understand which authentication and verification methods meet the Salesforce criteria for secure authentication.
Which three functions meet the Salesforce criteria for secure mfa?
Choose 3 answers

Universal containers (UC) has a mobile application that calls the salesforce REST API. In order to prevent users from having to enter their credentials everytime they use the app, UC has enabled the use of refresh Tokens as part of the salesforce connected App and updated their mobile app to take advantage of the refresh token. Even after enabling the refresh token, Users are still complaining that they have to enter their credentials once a day. What is the most likely cause of the issue?

An Identity architect works for a multinational, multi-brand organization. As they work with the organization to understand their Customer Identity and Access Management requirements, the identity architect learns that the brand experience is different for each of the customer's sub-brands and each of these branded experiences must be carried through the login experience depending on which sub-brand the user is logging into.
Which solution should the architect recommend to support scalability and reduce maintenance costs, if the organization has more than 150 sub-brands?

Universal Containers has multiple Salesforce instances where users receive emails from different instances. Users should be logged into the correct Salesforce instance authenticated by their IdP when clicking on an email link to a Salesforce record.
What should be enabled in Salesforce as a prerequisite?