"One of them will be assigned to you" το μεταφράζω ότι δεν υπάρχει περίπτωση να μην σου ανατεθεί κάποιο θέμα. Αν μπορείς ξαναστείλε της κάποιες ερωτήσεις:

How and when will I be aware of the fact that a specific topic is allocated to me? Because supervisors' consent to supervise me does not mean they actually will, according to the instructions.

Should I submit a project description to the supervisor even if the topic is not officially allocated to me yet? If yes, does the assignment of this topic depend on my project description submission?

Could you elaborate on the skype/hangout discussions please? Which phase of the project do you mean by skype/hangout discussions?

Και στους τρεις καθηγητές που δεν απάντησαν:

Dear Dr .... (ανάλογα με το θέμα)

I would be glad if you informed me about the availability of the .... θέμα topic Ι applied for.

Best regards