NEW, MAKING A GAME WITH A FEW QUESTIONS.

First, is it generally accepted to use premade graphics + the DLC to make a legit game? I don't wanna just look like some cheap guy who just uses other people's stuff.

It's fine. Some people will grump about RTP usage because they're big babies who think everyone should make everything custom, but if it fits your game and you use them well there should be no issue. The most you're likely to get is someone saying it'd look better custom but as long as the game plays and looks well there should be no issues. It's really more about how effectively you can use the resources rather than what the resources are.

There's quite a few tutorials around to help people get their skills in mapping up - here's one I link often, and this series of tutorials can help (especially the Shift Mapping one).

Secondly, about how long do people generally spend on their games? I intend to make mine about as long as adventure games in the vein of The Crooked Man and Mermaid Swamp.

Usually it takes as long as it takes. Some people have made games that took years. Some took months or weeks or days. Hell, I've even made one in 24 hours (albeit very short and more of a joke game). You can't really put a time-stamp on development time because there's no telling if things will pop up to change it.

Maybe you'll have a great idea that needs implementing. Maybe you'll run into a bug you don't know how to fix. Maybe you just want to polish the game up to a shine. That all takes time.

And sometimes you just don't have time to work on your game and that eats up time like a motherfucker.

Frankly, a good game that's at least an hour or two long should take a newbie between 2 weeks to 3 months, depending on how polished they want it to be and how high of a standard they hold themselves to.

Some people do a rush job of three days and they end up with a terrible game full of bugs and bad mapping. Don't aim for that. Take time to put in the effort required to make a great game and you won't be disappointed.

To sum up, it takes as long as it takes. Sorry if that's not very helpful. >.<;

Finally, how often do people actually use the RPG-battle part of the maker? Most of the games I've seen are like the aforementioned survival-horror games, without many actual battles.

As you mentioned, survival-horror games don't really use the default battle system often, probably because it breaks the immersion. You've built up a lot of in-game horror and suddenly you're in a new screen battling it out with an enemy with breaks in-between.

It gives the player a chance to breathe instead of on-map battles which involve building up the suspense - can you dodge past the enemy to grab the gun and line it up correctly to shoot it at the right time? Will you manage to make it to the other end of the hall while zombies and ghosts come jumping out at you, meanwhile dodging missing floor tiles?

On-map 'battles' keep you in the immersion. Cut away battles break it, which is probably why they aren't used as often.

Can you use them? Yeah, sure. Should you? That's a question you'll have to ask yourself.

author=cub149
Also I just got a problem.
A tile's blocked, but I can still walk on it, as pictured.

I randomly had a problem like that, only it was the other way around (i.e. being able to walk on a tile that was supposed to solid). I seem to recall right-clicking on a neighboring tile that I knew was solid, put it on the offending tile. Or something like that. Whatever I did, it was done rather quickly, and it seemed to work okay. Hopefully, your fix will be as quick.