No you can't
Not anymore
There is no Item ID for experience orbs in Minecraft. It does not go in your inventory, or you can't hold it in your hand. BUT you can use "Bottle of Enchanting" though, which is a potion that gives you experience, the same effect of an experience orb, it's ID is 384.
Magma Cubes, along with Slimes, are unique in Minecraft as when they die, they drop four smaller versions of themselves, and when they themselves die, they also drop four smaller versions of themselves. As well as this, Magma Cubes usually (not always) drop magma cream and experience orbs.
Me personally, the hallway to the Emperor's throne in The Land of The Dragons, because there they drop lots of orbs and you need orbs to get experience.
An item enchanted with the Mending enchantment, is capable of self-repair. When experience orbs are created, some of the experience will be absorbed by the weapon, and it will be repaired a little bit.
Enemies may drop HP orbs, MP orbs, Munny, or synthesis materials. Some enemies are even known to drop weapons, shields and accessories.
1 experience for small drive orbs and 3 experience for large orbs.
On any computer you should be able to see a long greyish bar at the bottom of the screen (right above your direct inventory) with each creature you successfully kill you will get some experience orbs; these orbs fill up your greyish bar, directly above your experience bar will be a number; this is your minecraft level, if your on 'creative mode' I'm pretty sure you won't have that bar. But you will in 'survival mode' and 'hardcore mode'. Hope I helped? If I'm entirely retarded... Someone, please correct me!
There are mods for basically ANYTHING you can think of. Yahoo/Google or go to YouTube.
In Minecraft, mending is an enchantment that allows players to repair their tools, weapons, or armor using experience points. When you collect experience orbs, the mending enchantment automatically converts those points to restore durability to the enchanted item instead of adding to your experience level. This makes it particularly useful for maintaining valuable gear over long periods without the need to use an anvil or crafting. Mending can be applied through an enchanting table, an anvil, or by trading with villagers.
Actually you don't need more than 20. Minecraft enchanting is all luck, you can actually get every natural enchantment on a pickaxe with level 25.
Yes and no. In the 1.8.1 patch, Notch released an experience system, and when you kill monsters they will drop some orbs. When you collect these orbs, a little bar under your food and health bar will rise. When it gets to the top, it will start over again. However, you don't really level up, and you don't get any more strength or better armor or anything. But this is probably something that Notch is working on, and hopefully it will be released in the next patch. EDIT: It is now confirmed that the ability to spend Skill Points will be added in the 1.9 patch.