Hey there! Welcome to the forums! It's good to see a wide range of people joining this forum from all walks of life <img src="smileys/smiley16.gif" border="0" align="middle" />
I strongly recommend checking out the manual, as it is very detailed and has been very helpful to me and everyone else on this forum.
1. Yep, this is certainly possible. The most simplest way of transitioning from one level to another would be the "Go to layout" action. Making a transition like from Zelda is something fairly straightforward too, I'm sure there's an example out there somewhere :P
2. Yep, Saving is totally possible too! I'm not exactly sure where the Save Data is stored exactly.
3. Making sprites move depends on how you want them to move. Platformer, Top-down view, ect. There are many built-in "behaviours" that speed this process up, they work very well!
4. Plugins are the things that people make to add extra capabilities to Construct 2 that weren't there previously. You won't really need to use extra plugins as you begin, as Construct 2 pretty much contains everything you need in order to make a game. <img src="smileys/smiley16.gif" border="0" align="middle" />
5. Storing items links in with "Variables". Variables are numbers that you don't neccicarily have to "see", but they are hidden away in the code and only you can choose to show them and use them. I'm not the best at explaining things, check out the manual :P
6. Yes! By default, monsters would reappear when you enter a room/return to an old one.
7. I believe that you can use the "Function" object to create your own scripts in a way. But, if you want a lot more freedom with what you can do, you'd have to have programming knowledge and write your own plugins.
8. There is some premade "templates" that you can use that the creators have supplied us with when you click "New" in Construct 2. Other than that, people share a lot of stuff on these forums, and there is a "tutorial" section where people post their tutorials.
Hope I was of use, and good luck on your game-making journey! <img src="smileys/smiley16.gif" border="0" align="middle" />