Sending bitcoin API questions I'm implementing the bitcoin sending API using blockchain.info for my website and have a couple questions.

Let's start with address A with an input of 10 BTC. I use API and pay Alice for 9BTC. 

Q1: The 1 BTC will return to my change address and unusable until the transaction is confirmed, correct? 
Q2: How the change address is managed on blockchain.info? 
Q3: If I turn on HD functionality, the change address is the HD generated address?

My plan is to use the input until it's almost run out, and then manually top-up from cold wallet.

Q4: So the transaction I sent to Alice or anyone else will always have 1 input, and 2 inputs (when I top up from cold wallet), is this correct?

Thank you
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