The only required field for a record in Salesforce to be synced or created as a prospect record in Marketing Cloud Account Engagement is the email address. Marketing Cloud Account Engagement uses the email address as the unique identifier for prospects, so it is mandatory for any record to sync between the two platforms. Other fields, such as name, company, or phone, are optional and can be mapped between Marketing Cloud Account Engagement and Salesforce, but they are not required for the sync to happen. For more details --->123

A completion action on a custom redirect will be triggered when an existing prospect clicks on the custom redirect. A custom redirect is a trackable link that can be used to measure the engagement of prospects with external content, such as a website, a PDF, or a video. A completion action is an automated task that can be performed after a prospect takes a certain action, such as clicking on a custom redirect.Completion actions for custom redirects will only apply to existing prospects, meaning prospects who have already been identified by Marketing Cloud Account Engagement through a form, a landing page, or an email4. Reference:Marketing Cloud Account Engagement Custom Redirects

In order to send an autoresponder email, you need to create an email template in Marketing Cloud Account Engagement and select the option ''Autoresponder emails'' under ''Available For''. An email template is a preformatted email that you can use to create and send emails quickly and easily.An autoresponder email is an email that is triggered automatically whenever a prospect engages with your marketing assets, such as filling out a form or downloading a file

What happens to the wait time when a user pauses an engagement studio program and the prospect still has time remaining on the wait period is that the wait time is paused and the prospect will finish the remaining wait time when the program resumes and proceed to the next step. An engagement studio program is a program that automates the delivery of emails and other actions based on the behavior and criteria of the prospects. A wait time is a period of time that the program waits before executing the next step. When a user pauses an engagement studio program, the prospects in the program are also paused and their wait times are not affected. Therefore, when the user resumes the program, the prospects resume from where they left off and finish the remaining wait time before moving to the next step. The other options are not what happens to the wait time when a user pauses an engagement studio program.Reference[Engagement Studio FAQ]

The best way to be able to track the number of visitors who access a file on a web page that the company does not own is to use a custom redirect. A custom redirect is a Marketing Cloud Account Engagement feature that allows you to track any link on your website or a third-party website and measure the clicks and conversions. You can create a custom redirect for the link to the file and use the custom redirect URL instead of the original link on your web page. This way, you can track how many visitors click on the link and access the file, and also see which prospects are interested in the file. A Marketing Cloud Account Engagement form, a Marketing Cloud Account Engagement tracking code, or a page action are not suitable for this purpose, as they are used for different scenarios. A Marketing Cloud Account Engagement form is used to collect visitor information and convert them to prospects. A Marketing Cloud Account Engagement tracking code is used to track the page views and activities of visitors and prospects on your own website. A page action is used to perform certain actions when a prospect views a specific page on your website.ReferenceCustom Redirects