What does the number at the corner of an item represent?

Do items level up? and if they do, what kind of benefits do they receive?

The number in the corner (if your talking about consumable items) is how many you have, consumables -like potions- stack.
As far as I've noticed items don't level, but you can 'trade in' items for better ones, for example:
You buy the +50 armor for ~700 gold, and the crit cloak for ~800 gold. You can then later buy an item that builds on those for less then you would buying it without those items, however you do lose the cloak and armor in trade.
So it works like an upgrade/replace system, or you could just say that you're selling your items back and buying the upgrade in one click.

Yesterday was my first day playing, I chose Master Yi for my first online match. Before you start the match you pick those 2 akills/powers. They had teleport and blind preselected for me so i kept them. I couldn't figure out how to use blind on an opponent, is it not an actual ability that i select who to target with it?

If you look on the first page of this thread, I believe someone said you can press "y" to unlock your camera and move it around

Thk!

nice to know basics like these, congratulations

How can i put items i have in my inventory to the ground?
When my 6 slots r full and i just need the recipe for an item combination, do i really have to sell another item for free place?!?!

Ah k!
Cool thx! :-)