You can't, unless you're using mods.
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You can make a diamond sword in Minecraft by placing two diamonds above a stick in the crafting table.
You need the Aether mod.
Have a sword. make an enchanting table. Have levels. Put the sword in the enchanting table. Click a available enchantment. BOOM a better sword. Bookshelfs gives you better enchantments for higher levels
You mine gravel, sometimes flint is dropped when you break a block of gravel.
With any block except sand or gravel. Use your imagination and show us on Youtube!