A: Hello,
you can segment your list of contacts in many different ways when sending a campaign. Yes you can decide to send a campaign only to the subscribers who opened previous emails inthe last 30 days.
In journes you can set steps based on the subscribers' interactions on the email content. The feature by which you will be able to set a new step on the journey based on the click on the specific link in an email will be released in about 20 days from today. At this stage, you can choose to set up a new step in the journey based on clicks made on any link in the email. To set up a new step based on a click on a specific link, you will need to wait for the release of the new feature I mentioned above.