[otrs] Prevent user reopening a ticket

Hello, I need to deploy a ticket system in two weeks so I have to quickly try the best alternatives, so please, forgive if the questions are too easy or have already been answered. The main question would be: Can I prevent that a user reopens a closed ticket? I'd need that the user could close itself its ticket for the case he is able to solve his problem, so I can't simply remove the status field from the interface. And a stupid question: when a user opens a ticket, he can choose the 'to' (I refer to the customer demo) field of the ticket, can't he? I'd need that the user could choose between two different kind of problems so I had thought to create two different account for them. Thanks in advance and sorry my English, Jean