Redeemed minecraft gift card, can only play demo

I keep going in circles… Signing in, took awhile, registering again only to find out i'm registered…
but there isn't a button that says play game…
read the trouble shooting articles… On topic…
need help… Answer is probably obvious… Just can't see what to do or where to go or what the problem is

What should I look for in a desktop to play games?

I need to get a desktop for my 13 year old to play games. Mostly Minecraft and COD Ghosts. I can't spend a lot and will probably get a refurbished one on Ebay. What should I look for as far as memory, speed, etc?

My grades dropped really badly?

My overall average went from a 92 to a 84 throughout the semesters.

I'm always known as the studious and nerdy kid, and now I'm failing one subject. I don't feel like myself anymore. I'm ashamed because I let procrastination and anxiety get ahead of me for once, and i'm only in middle school.

I know i'm sounding whiny and just a lazy person but I think the reason behind it is because of games, ever since I found online games for animes and minecraft etc, I felt that I want to become a gamer and it's effecting my grades.

Minecraft S and W keys not working?

I just recently downloaded the Technic Launcher to Minecraft and I have been playing Hexxit. This morning I had nothing to do so I played for around 4 hours. Soon after I noticed I would stop sprinting after I had started. Then it got worse to the point where the S and W key ( The ones that I use to move forwards and backwards) copmpletely stopped working. My character froze and I couldn't move. I could go left and right and I could jump, but the S and W just wouldn't work. I opened the chat menu to type, and they still wouldn't work. Eventually I closed down Minecraft and went to google, nothing changed the keys still wouldn't work. After a while they worked again, so I hopped back on Minecraft and tried another time, It worked for about 10 minutes before they stopped again. I have tried everything I know how to do. I even launched normal Minecraft, and nothing changed. I have a Toshiba laptop so I can't go buy a new keyboard( Maybe I can, i'm not to sure) I've tried shutting it down, restarting it, removing the battery, and holding down the ON button. Nothing works. Sorry for the long paragraph but I really don't know what to do. Any help would be much appreciated. Thank you.

Added (1). Bb Major, yes they work fine outside of Minecraft. But, if I leave Minecraft right after it begins, then they won't work. Only after I hit SHIFT and CAPS LOCK does it return to normal.

I'm a PC gamer and I need a laptop that's decent with games?

I need a laptop for playing games. Reason I need a laptop is because my parents are divorced and I go to my dad's house every other weekend. I need mobile Power! I need a laptop that can play Minecraft well. I have an old Acer desktop From 2011. Let's just say it can't handle Minecraft very well. I do not only play Minecraft though. I play L4D2, Mirrors Edge, Portal 1 & 2, Terraria, e.c.t. I was thinking about http://www.bestbuy.com/...cp=1&lp=29 (If the link is messed up i'm sorry) Or http://www.bestbuy.com/...cp=1&lp=21
(I prefer AMD) I'm open to any computer as long as its 450 dollars or less! This is very important! I will take any other laptop as long as it isn't Toshiba. I have had many issues with Toshiba in the past and to be honest I don't like the company. Anyways thanks for helping!