I am planning my trip to Istanbul to Athens via ferry. I will stop by two Greece islands along my way. Can anyone tell me what will be the best way to do that?

How advance do I have to buy or reserve ferry ticket?

What are the best companies?

How many days I should counts for traveling between Istanbul-Athens other than stay?

Any recommendation about islands? I am not very beach person but I care about view and archaeological facts.

Any suggestions would be greatly appreciated :)

Thanks !!