So, I'm trying to make some maps, but I can't access all of the terrain options in the terrain tab. There is no way to scroll through them or switch between pages of terrains, meaning that about half of the terrains (Cliff, Special, and who knows what else) are inaccessible to me. Does anyone know of a way to access the terrains? I'm also opening this as an issue for A28, even if it doesn't get fixed till A29.

It's R28 But you can start porting your mods, there won't be big changes anymore breaking compatibility.

So, is there any idea of how much time is left until A28 become the current version, i.e. replaces A27 on the main website, and I have to port all of my mods over to it? And, when that happens, what changes will I need to make for my mod(s) to work on A28, if any? I know that A26-A27 had some changes, specifically regarding the simulation code, what stuff is changed for A28?

Will do.  I think leaving the fortress and arsenal out is a good choice, since (being somewhat of a noob player still) I was losing to the AI when it was building fortresses, and since I disabled siege weapons from being trained (which again, I Iost because of them), arsenals are somewhat useless. I'm testing the AI on some friends of mine, who are also noobs, so I'm actually getting a pretty good idea of what is too powerful or too weak. Which AI? Mine, the custom Hyrule ones I wrote, or Petra?