Thanks guys 
So if I wanted to, I could take my wallet address and private key from bitcoin-qt and import into blockchain (or any other online host which allows imports) and spend its contents?? The software (if offline) or hosting website (if online) is actually irrelevant as they are only means to send, receive and view your bitcoins. All I need are these two pieces of information.
So if I wanted to, I could take my wallet address and private key from bitcoin-qt and import into blockchain (or any other online host which allows imports) and spend its contents?? The software (if offline) or hosting website (if online) is actually irrelevant as they are only means to send, receive and view your bitcoins. All I need are these two pieces of information.
Yes, that's correct.
(You could even do with only the private key, the address to receive coins is derived from it - it just doesn't work in the opposite direction).
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The other thing I haven't seen much information about is a sandbox where you can 'play' with virtual bitcoins and get to know what you are doing without risking your real bitcoins.
Does this exist? Has anyone come across such a thing?
There is a Bitcoin testnet, but I haven't tried it.Does this exist? Has anyone come across such a thing?
Most faucets/free sites arent that good to test that stuff anymore, they give out too small amounts, it takes a week until they finally send something or they just give nothing. I did a lot of my tests with transactions from bitvisitor.com, maybe this is still good to go.
Just make sure it's enough to pay the fees (usually 0.0001 Btc) per transaction.
Or you could buy e.g. 0.5 Bitcoins and use small amounts to test all you want to.