Can an iPhone 6 Plus be repaired under apple's limited warranty?

So today I purchased an iPhone 6 Plus from a person on Craigslist. I got a great deal on it. However, this device has a hardware malfunction. The Touch-ID doesn't work. Not to mention, there's also a tiny barely visible crack on the top right hand corner of the screen. The ring/silent switch is also broken. I looked up the serial number and fortunately this device is still under Apple's Limited Warranty! Is it possibly for me to simply take the device to the store and have it repaired or switched out? I don't think the owner realized he could have taken it to get fixed. And if so, does the apple-rep ask for my personal info to verify?

Added (1). Thank you in advanced.

Who needs to sign for a package thats delivered to your house?

My mom ordered a new iPhone online and it is supposed to be delivered to our house tomorrow. She will be at work during the day but I will be home. Could I sign for it even though it's not my name on the package? Does my age matter as I'm only 15?

Was Sold a Stolen iPhone 6

Is there any way I can Jail break or do something to make the iPhone I was sold work? When I try to set up my settings, after they ask for my Wi-Fi it say's I need to put in the current iCloud account but I don't know it because it was sold to me like that. I have no way to contact the seller. Is there anything I can do to unlock it, jailbreak it, or something?

How to take cash out of my credit card?

I'm on this trip and I need a new phone, a friend offered me an iphone for $150 and said I'd buy it. The problem is I only have my credit card on this trip. How do I take cash out of the credit card?

Is there a middle finger emoji?

I have a Android and can't see most of the hand sign emojis. I see people use hand emojis, but to the side are [X].
People with iPhone: please type in the hand emojis please