I would like to ask you about the correct behaviour when applying at different universities for different PhD positions.
Currently, I won two PhD positions and a second shortlist for a third one. The third one is the one I really want, but the interview will be held on campus and due to coronavirus pandemic it has been postponed after the mid of August. I have strong academic and personal reasons to go for the third one, but of course I am not sure that I will win it. Now I have to decide between the two I already have. I would feel guilty to tell yes to one of them and later on withdraw the offer.
What is the acceptable time to change your mind? Should someone follow his personal motivations or be ethical?