Nice. I think your hills came out pretty well.

Some default may not be appropriate when running it on a different user than the one who installed it, but CC3+ does remember the last directory used, so once you save your map in a proper location, CC3+ should remember that for the next time. I am guessing that it probably default to the installation directory, where a normal user won't have write access.

Your point 1 is of outmost importance. Always have an idea for what you want to make. Just a rough idea with a few concepts is good enough, but never just "start a dungeon". Have a little thought about your desired layout, or perhaps a central feature you want to develop the dungeon around, or something....

I've noticed that myself. I think it is because rocks are nocturnal and can't grow in the light, they start growing once you cover them with your sleeping mat.

Looks like a great start. Looking forward to how this will turn out. This style can really look nice.