It’s an alternate timeline. You’re right about Link pulling the Master Sword as a kid in BotW, but that was BotW. AoC doesn’t contradict BotW at all because it’s an alternate timeline. Events and backstories aren’t the same.
The existing buildings barely changed much. Hyrule in those 100 years was too busy trying to stay alive to think about innovating and renovation of existing buildings. Also, Zora's Domain specifically is said to have existed in that state for 10,000 years. The artistry of the domain was one...
The Great Calamity devastated Hyrule Field and the only Hylian settlements to survive were Hateno and Lurelin. The other races were so far out that they survived it mostly. We do know, though, that they had to fend off Guardian attacks for a while. There are lots of dead ones on the road to...