I have the below requirement from my support team, Please let me know if this is possible through apex coding. Thanks in Advance.

When a user select 'Send An Email' from case, Attachments in all the existing emails related to this case should get attached to the email being sent.

I have installed a managed oackage in my org and now i want to upgrade it. This app access is controlled by licence and permission set.  When i click on the upgrade link, Below 3 options are displayed,
1. Install for admin only
2. Install for All Users
3. Install for Specific profile.

Which option should i select? Not all users assigned to same profile have access to this app. So i think chosing the 3rd option will not be correct. 
If i select 'Install for admin only', will the licence be revoked from all the other users?

Thank you for your help in advance.

I have installed a managed oackage in my org and now i want to upgrade it. This app access is controlled by licence and permission set.  When i click on the upgrade link, Below 3 options are displayed,
1. Install for admin only
2. Install for All Users
3. Install for Specific profile.

Which option should i select? Not all users assigned to same profile have access to this app. So i think chosing the 3rd option will not be correct. 
If i select 'Install for admin only', will the licence be revoked from all the other users?

Thank you for your help in advance.

I have the below requirement from my support team, Please let me know if this is possible through apex coding. Thanks in Advance.

When a user select 'Send An Email' from case, Attachments in all the existing emails related to this case should get attached to the email being sent.

We do get emails with or with out attachments (payment confirmations details ) from the clients, to our email to case routing emails address that generates the case. And our advisers will print that emails attachments and copy the body of email in separate sheet print it out and scan the copies and send that to Payment allocation 3rd Party system. We want to avoid the manual process and forward that email to our 3rd party system with or with out attachments and close the case with some closer reason and change the owner to user. My Question is is it possible to Forward email with attachment to 3rd party email address. If any one Knows please helpe me.