1.diamonds in the default game are light blue and a little ovalish
if you want to know what they are in texture packs, open a creative world and open your inventory, look at the compass in the top right of the gui, click on it, and type diamond, there should be the diamond of that texture, this is true for any item. unless you mean on planet minecraft, they act like votes. if people like what you've done then they will most likely give yo a diamond.
2. there is a way, search on websites for minecraft servers, look for a fairly big one, this will ensure that people know you. another way is to get some video recording software such as bandicam or fraps, and create a youtube channel which has you playing minecraft with good commentary. on planet minecraft it is hard to be known well, due to the fact that there are loads of people on the website. but you can post things to get people on here to know you actually exist
3. leveling up in the game of minecraft is shown above your "hot-bar" or item bar at the bottom of the screen, it is green when filled and usually has a number above it, that number is your level the leveling system allows you to "enchant" items like swords, tools, or any armour. that will remove your levels. the way you increase your levels is you kill "mobs" or monsters such as skeletons (skeles) zombies, creepers, silverfish, and the latest mob that will soon be added tho the game the whither, now these are just examples, other mobs are in the game as well i just wnted to state the most basic mobs. leveling up on planet minecraft, you have to post your own texture pack or mod, you can also post skins etc. basically you must do lots of stuff on here to level up.
if you have any questions further please PM me or look it up on minecraftwiki,com
