1. Wolves age one year on the first day of spring, no matter when they were born. Since each season last three real life days, wolves will age a year every 12 days.
2. Do you mean other terrains? You will unlock a terrain for every ten territory levels you complete, so you can only explore in forest for now, and after completing 10 levels, you can explore in the next terrain (swamp).
3. Yes, they can interbreed. There are no consequences / increased risk for defects for doing so; however, some players prefer having only clean lined (not inbred) wolves.