If you have cheats turned on (which you do when you create your world), open the chat box with t and type /weather clear
Chat with our AI personalities
Snow can go away in minecrafts, and can melt very slowly but it will still melt in the category its in on or by the minecraft.
You cant make it snow or rain. For snow you must be in a Tundra biome (the ones that are coverd in snow and have spruce trees) any time its raining, go over to that biome and it will be snowing!
Dropped items will eventually despawn. The amount of time it takes differs, they go away more quickly if you move further away from them.
You cant go to Olympus but you can go to the nether.
go to options, and force update. this will restore your minecraft jar and make it run again.