Will Apple replace my iPhone 4? - 2

I got my iPhone 4 in December 2012. A couple of months ago, my sleep/wake button stopped working. I didn't drop it or anything at all. One second it worked, then five minutes later it couldn't be pressed down at all. This made me really angry, and I had to start using AssitiveTouch to start turning the screen off and plugging in the charger to turn the phone on. A few days ago, I was using my phone, it had been working fine all day, and then I picked it up to call someone and it was off. I tried to charge it all night and it didn't come on at all. I tried everything, like restoring it, and the computer wouldn't even recognize it because it won't come on at all.

If I take it to Apple, since its only been six months and I still have the standard warranty, will they replace it on the grounds of manufacturing errors, because both of these things happened randomly out of nowhere, or would it have to be paid for? Other than that, there's nothing wrong with it besides some scratches and little chips on the corners. I don't think it should have to be paid for because these are manufacturing errors, but I feel like Apple won't let it go that easy? And I don't have an appointment, so if we just walk in, will they just send me away cause I didn't make one?

I think they will change it. Make sure that the water indicators have not changed. You also need proof at the store that your iPhone has the problem.

Regarding the appointment, you should just make one instead of wasting your time and money walking into the store. Just make an appointment since it's free. I'm quite sure they would change your phone because there's no reason not to.