Sending bitcoin API questions
If you have 10 Bitcoin, and pay Alice 9, the 9 will be unusable by either party until the transaction has been confirmed, them Alice will be able to use the 9 Bitcoin.
Since you only sent 9, you will still have 1 Bitcoin in your account that will be useable and available, no matter if the 9 Bitcoin transaction have been confirmed yet or not.

I'm not sure what you meant by the second question, but blockchain.info has a great explanation on how to use and change and import wallet addresses and other info here. You can also look up more info if needed.

A Hierarchical Deterministic wallet is just a wallet that you can back up and restore with a mnemonic, using 12 common English words. If you press the &quot;backup funds&quot; option, you can store these words to later restore your wallet if you lose it or etc. FYI, the wallet stores all the addresses you've had previously, so when you backup your wallet you backup all your addresses on the same account

Not if you run out of Bitcoin on your &quot;cold&quot; wallet, you won't have anything to &quot;top up&quot; on. If you decide to send 9 Bitcoin to Alice and your top up is 1 additional BTC, to reach 10, why would you do 2 separate transactions, one from wallet A and one from cold wallet? Wouldn't you want to just do 1 transaction of 10?


Happy Bitcoining