Byzantium never falls

We all know the date - 1453. The ottomans conquer Constantinople and the ottoman empire becomes greater. But what if, say, when the ottomans began attacking the Byzantines, they could've been prepared and manage to retake the ottoman lands?

Is this a question or?

Greece and Asia Minor would've for sure been exhausted from war so I would think that there would be a period of peace and slow recovery. However, I do think that the Balkan states like Serbia, Bosnia, and Wallachia would be annexed back into the empire.

The Mamluks in Syria and Egypt would probably come into conflict with the Byzantine Empire but I don't think that too much would've changed between them.

From there on, nation-states were being established (France, England, Poland, Russia, etc.) and Byzantium would be among them, with deep Greek cultural ties that would unite the empire but serious reforms would have to be made to keep up with the Great Powers.

I made a map and a nice thread about that on this board. You can check it out if you want.
It's not exactly the same, but it's pretty similar

It was possible but I don't think Byzantium was long for this world at that point. Mehmet II needed Constantinople to fall to ensure the stability of his empire. I read in one historical novel "1453" that Mehmet couldn't afford to be bunkered down in a long siege because the unity of his diverse army (which included quite a few Christian soldiers and mercs) would dissolve if it took too long. Keeping that in mind, the Byzantine defenders could have held out for longer but they made a mistake during the siege and accidentally left one of their gates open giving the Ottomans the opportunity to exploit the gap. If Constantinople withstood the siege and the Ottomans fell apart from the failure I doubt the Byzantines could take advantage of the chaos. Byzantium was extremely week in the decades leading up to 1453. Much of the late 14th century was rife with civil war between the emperor and various pretenders in Byzantium

If the ottomans failed, they would try again.  Or, if this defeat was decisive enough to permanently weaken the ottomans, another country would just take their place and take Constantinople instead.  One thing to think about though was what if a christian country took over the city and became a major power.  How would it shape Southern Europe and Turkey and the Middle East without the ottomans controlling the lands for centuries?

The technological superiority of the ottoman army was way greater than the byzantines. Since the ottomans had cannons i would only be a matter of time before constantinoples walls would fall.

But if the byzantines would get help from european allies they might have lasted for a few more years as the ottomans werent doing all that well.