Question: Do you think, if he had really wanted to run away, he could have? If your answer is yes, why didn't he run away?

Your question is an opinion question which means that there is no right or wrong answer; therefore, you should figure out your own thoughts when you compile your own essay.  This being said, I think that Misha could have run away at any time.  The reason why he doesn't is that what he clings to most is identity, and all of the characters he stays with give him something in regards to that identity.

The...

Your question is an opinion question which means that there is no right or wrong answer; therefore, you should figure out your own thoughts when you compile your own essay.  This being said, I think that Misha could have run away at any time.  The reason why he doesn't is that what he clings to most is identity, and all of the characters he stays with give him something in regards to that identity.

The actual proof behind my opinion is that Misha does run away whenever he wants or needs to (in and out of the Warsaw ghetto).  This is at the point of the story where Misha is helping Janina and her family as they are "relocated" to this dreadful place.  Of course, there are other times where Misha can (and often does) run away as well.  Even before he is given his identity as "Misha" he is often running from people he steals from.  In fact, he is doing so in the very opening scene of the book.  I guess one could even say that he "runs" from Uri and the boys (and that safety) to move with Janina into the ghetto, following the first identity of friendship he's ever known.

In conclusion, it is safe to say that, yes, Misha could have run away (and often does), but values both identity and friendship more than the danger that he often doesn't know that he is in because of his innocence.