I can't destroy blocks in Minecraft Creative Mode (singleplayer)

I just logged in to Minecraft after maybe 8-9 months at the most. When I first logged in, I tried to switch between modes but I forgot how, so I looked for it and it said to press F1. Before I did I could destroy and place blocks, but now I can't destroy them! Is this common, and does anyone know how to fix it?
And btw, whenever I go onto a bare hand to destroy something, it just goes back to the first item in my inventory.
Best Answer
First things first.
F1 makes your Minecraft become into like a Camera Mode. It removes your inventory and hand that you can see again if you press F1 again.
Next.
If you cannot destroy blocks, either you are holding a sword, or you are in Adventure Mode.
You can change back by executing the command (pre 1.13):
/gamemode 1
Edit: The new command post 1.13 is:
/gamemode creative
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How do you get rid of blocks in Minecraft Creative?
Bedrock is a block that is normally indestructible in Survival.Nas - I Can (Official HD Video)
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Answer 2
Try not to keep a sword in your hand while trying to break blocks,because they won't. Attack with your empty hand or with another object.
Answer 3
You could be in spectator mode or adventure mode. You should be able to go into creative mode by using /gamemode 1 on a world with cheats
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