From the screenshots they don't look like out of box Landing page Content templates. They seem more OOB Email content templates. If you are seeing these templates in your landing page content library, please raise a support ticket with Adobe. May I know the version of your ACS instance?

Inside the Landing page click Change Content -> Address Acquisition. This landing page template already has Country.

Is there a notification process available in ACS Email Designer to alert the users on who else is in Edit mode if multiple users are editing  the same Email content at the same time in the HTML Editor? In that case the user can contact the other users to avoid overriding each other's change.

There is no JS Activity in ACS to use Workflows, so I don't think there is much we can do with javascript other than using it in content blocks.

I was trying to explore the merge profiles function of ACC. Is there any online link available describing that feature? It will be helpful if you can share.Regarding Unsubscription, aren't your profiles tied to a Service in ACS? when someone unsubscribes shouldn't the profile unsubscribe from that s...

Are you seeing the tracking info of opens / clicks against the same delivery email for which it is hard bounced??If they are black listed that means the user have opted out of email channel. In that case the profile's email address is good and he/she might have received & opened the email prior to b...

If you want to restrict the sensitive data, you can store that in a custom schema and assign this to a Org unit which the user's group is not part of.

This feature is already available now. Please check the below linkAdobe Campaign Help | Creating a custom profile dimension

I have not tried this but I think we can do this by using the Package Import feature of ACS. Get the Schema XML from ACC and try to import it to ACS using Import Utility. We may need to modify the XML depending on the error it throws.

I am not sure how you are planning to change the id but I don't think it is a good idea to change the id field manually in the back end. May be you can raise a support ticket to confirm this with Tech Ops team.