Not a chance.
Not a chance. The Sasasnids would need have a fleet in the Black Sea, and more importantly, one that can go toe to toe with the Roman fleet.
Unless they can do what the Arabs did and hold Egypt for several decades and build a fleet there, they're out of luck.
Why would you need Egypt? What's wrong with Syria?
Not yet,Greek Fire didn't debut until after large portions of the East were overrun during Arab-Byzantine Wars.Not just the fact that the Roman Navy has Greek Fire, I think its more so the case that the fact that the Romans have a Navy in general is the reason why it's pretty much ASB for the Sasanians to conquer Constantinople. The Sasanians were primarily a land power. (In fact, I have not found any sources that said that the Sasanians had a navy, let alone one with a significant presence.)
Frankly, I feel you have a better chance partitioning the Empire between Sasanian Asia and Africa and Avar Greece and Thrace, besides it's not like Khosrau actually wants to take Greece as a grudge against the failures of the Greco-Persian Wars over a thousand years ago...right?
Not yet,Greek Fire didn't debut until after large portions of the East were overrun during Arab-Byzantine Wars.
Incendiary weapons aren't new,but they aren't Greek Fire.Greek Fire was produced by a refugee who fled Phoenicia after the Arabd conquered said province.Doesn't Procopius discuss something quite similar in his accounts of Belisarius' campaigns?
As for the OP: I'm inclined to agree that it's pretty difficult for the Sasanians to have a good shot at conquering Constantinople. I'd suggest you'd need at the very least total naval supremacy as the Venetians and Ottomans both had later on, which requires sustained Iranian occupation of the eastern Mediterranean ports. On top of that, the walls themselves have to be overcome: possibly the city could fall to a Sasanian-backed pretender and then the Sasanians themselves? Remember that the Iranians will also be operating at the end of a very long supply chain.