When you decide to carry on this experience you do not obtain the status of exchange student (not even if you spend a certain period at Universities with which UNIBO stipulated an exchange agreement).
You should contact the University you are interested in on your own, asking if they provide for this kind of possibility and at what conditions.
As far as UNIBO is concerned, there is no standard authorization procedure by your Degree Programme Board to leave and carry out this kind of experience abroad. Therefore, UNIBO will not provide a nomination letter. In other words, leaving as a visiting student/free mover does not entail any administrative support by UNIBO International Relations Offices, be it about contacting the host University or supporting you in addressing issues related to your Degree Programme. UNIBO does not provide any funding to free movers.
If you are interested in the recognition of credits obtained abroad, you should follow the procedure mentioned in the page “Shortening of the degree programme” upon returning. That is to say, submitting to the Student Administration Office a series of forms relative to the activities carried out abroad, translated into Italian and legalized when needed. Upon verification of the forms, the Student Administration Office will ask for the recognition of credits to the Degree Programme Board.
You can also try to contact your Degree Programme Director submitting a formal request to the Degree Programme Board beforehand, i.e. making an agreement about the exams to carry out abroad before leaving. However, we remind that there is no routine procedure, and therefore there is no guarantee that the Board decides in favour of a possible recognition prior to departure.