Hi Nikos, thanks for your feedback :) In answer to your questions:
1) The homepage will show the tickets posted, however whether or not users can access the information will depend on your settings. You can choose to "Protect" them, so when they try to access a ticket that is not assigned to them, they will receive the message "Sorry, you are not assigned to this ticket, and therefore cannot view it". You can also choose read only or read/edit if you wish. Also, depending on their permissions, they may not be able to see the "Create Ticket" link.
2) If someone has the ability to close a ticket, then they will be able to re-open it, so closing it permanently would be achieved by changing either the users permissions (which is not good if you need them to keep logging tickets), or change the assigment of the ticket.
3) User information can be edited by the user in their WordPress
profile screen. Initially though, you are only required to create a username and enter the email address and password when setting them up.
4) Yes, permissions to tickets depends on the ticket assignments and the users access. Thanks.