If you have a 2 button mouse it will be the right button. Just click it once for one item.
you right click on a block
right mouse click
click the b button when the item you want to drop is in your hand
Minecraft's Item ID's can be found on Minecraft Wiki. Link in related links.
A clock in Minecraft is a handheld item, it can't be placed like a decorative block. However what you can do is craft an Item Frame and put that on the wall, then put the clock on the item frame. That way you then have a wall-mounted clock.
Minecraft only lets you stack most items to 64, you cant place 64 different item in your inventory only 36 stacks of items. (if that's what you meant)just collect 64 of the item. not all items stack to 64 unless your using a mod that lets you.
Press your inventory button and you see 4 squares next to your character. That's how you craft things.
Select an edible item eg. Cooked Porkchop or Mushroom Soup and hold down the right mouse button.
Press the A button repeatedly near the spot the itemfinder is leading too.
Put an eatable item on the action bar and select it with the hotkeys. Then just click and hold down right mouse button, and you will eat the item and fill up your food bar.
Yes. Slime ball, enderpearl, eye of the ender... but you can`t place any of them.
No, you can't take one item from a Minecraft mod unless there is a separate mod which contains that one item.