"İstanbul changed a lot."
Translation:İstanbul çok değişti.
Your Turkish question is correct my friend. Grammar & meaning very clear. A like ^ & lingot from me. It's worth waiting two years for someone to notice a very good topic comment.
Appropriate to the topic too.
I think this was a posthumous comment as in non active learner.
No, that would be exactly like saying: "It was changed Istanbul a lot." i.e.; ungrammatical. "değiştirilmek" is in the passive voice, which means Istanbul is tge subject now: (Istanbul was changed). You can't add the accusative suffix anymore. It can't both be the subject and the object at the same time. Passive verbs can't have objects.