How to disable pop3, do access to imap only from 1 ip, disable delete and answer via roundcube

Hello everybody!
There are need to added some mods to exim and roundcube

  1. There is an admin who can connect to the server from his ip by imap
    Need to turn off Pop3 and allow connect to imap only from white list of ip
    Admin has address - [email protected]
  2. There are many users
    user1
    user2
    user3…domain.com
  3. They can use only web access via roundcube
  4. Is it possible to close opportinity to delete any letters and answer for them via roudcube? only receive and read
  5. But admin can do any actions by imap for they boxes

Thank you for advises!