5 Month old bike, pedals and brake issue got a Merida Matts 40-D bike in September/October, now I'm having some issues and need some help fixing them. Bearing in mind I've had this bike that long, I didn't start riding it until mid October and I stopped riding it between mid December and mid January. 

Firstly when I first got the bike one pedal was ever so slightly stiffer than the other, I thought nothing of it but about 3 weeks ago the pedal became stiff, so I decided I would re-grease the pedal, did it all, seemed better and then the next day went stiff again. Re-greased it again, this time even freer than the one that is fine, day later it went stiff again. It's so stiff that unless you push on the pedal all the time it flips underfoot. Any ways to fix it without getting new pedals?

After my xmas holidays my brakes started to loudly squeal, so I bought the stuff to sand down my pads slightly and to bleed my brakes. I have just got around to bleeding them, they seemed much better to start with but now squeal again. What can I do to fix this?

My chain also seems to look odd, unlike any chain I've seen before, it seems as if the outer links are bent outwards slightly. I don't know if this is supposed to be like it?

I am thinking I should just try and send the bicycle back for a refund, I ride it every day for 5 minutes back and to University, I really didn't expect the bicycle I paid £250 for to have these issues so quick.
There's going to be a limit to what you can do to fix it without spending money on new parts. The bearings in your pedal for instance might have seized - you could take the pedal apart and regrease the bearings, but if they're toast then you'll have to buy either replacement bearings themselves or pay a few quid for a new pedal entirely. 

TBH if I were you I'd take the bike back for a refund and spend that £250 on something second-hand instead. You can get a nice-ish older bike for that kind of money with much better quality parts.