Is this mod compatible with Extended Timeline?
No, unfortunately not, since both mods change the map in some way. Mods with province or area specific events/missions/decisions also won't work

Will you remove the ice from the poles?
Will you make deserts/coasts greener?
Will you add more colonizable province along the new coasts?
Despite the fact that the sea levels rise to 75m, like what would happen if all ice on earth melted, I don't plan on making climate change the cause, meaning the earth isn't warmer than it was irl. Additionally, I have done some light research into the effects of these new sea levels on the climate, and in general the new bodies of water don't seem to affect it much overall. While there might be regional changes, they are hard to predict and I'm no meteorologist, so I chose to ignore them. However, if I can find solid evidence that there would be noticeable changes in certain regions, I will likely add those.

Why does Egypt look like this?
Except for a few oases, all towns and cities in lower Egypt lie on the coast, in the Nile Delta or in the Nile flood plain, all of which are below 75m. The remaining desert is only very sparsely inhabited by nomads, over which the Mameluks had little to no control irl, so I decided to have those province uncolonized

Will you create a mod that lowers sea levels?
No, most likely not. I want to focus on this mod for the forseeable future and another mod of this scope would be a lot of work