Quick answer. You are correct on this. You can never book a trip 355 days out from first leg because even if you plan to change all the dates, when you first book the last leg has to be at least 10 days after first departure.

So lets assume all airlines release their flights 365 days out. If you want to start the trip on 3/12/21 you can not really book that first flight until 3/22/20 because you have to book it for 10 days and last flight will not open up until then. All that being said. If you packed it all into an initial 10 day itinerary you can theoretically risk it and change dates as you go. Of course you risk having to cancel the entire thing and start over if one of the "change to dates" does not open up like you expect. You can not take an existing itinerary and do anything but change dates. To add something in or change a city you have to cancel and start over and the seats you cancel do not necessarily show back up while re-booking as you say.

Looking at your chart release date of ANA and Turkish works in your favor but Ethiaopian and Thai are an issue on April 14th and no way to move that up 9 days.

Not that it exactly applies but I booked an ANA flight HND-ORD on June 7th, 2018 for a flight March 13th, 2019. 277 days apart. This was THREE seats in business class.

John