I got the confusion when someone said that if you keep using the same address over and over again then your wallet can get hacked.
Ye, lots of people are talking nonsense.
The good thing is, that you now can make sure to never ever believe these people because they have shown to be incapable of understanding the fundamentals of BTC.
Now I still don't understand the following:
1. one wallet can have many addresses: i've tested this it's easy to confirm
A wallet is just a piece of software which manages your private-/public keypairs.
So, yes. A single "wallet" handles multiple keypairs and therefore addresses.
2. The number of Bitcoins is contained in the Wallet, not in a particular address: not sure?
I'm not sure what you exactly are asking for.
Most wallets do show the total balance somewhere, including core. It is calculated by adding all the individual
balances a.k.a. unspent outputs together.
3. I don't need to create a new wallet.dat, i only need to create a new address in the same wallet.dat: not sure?
You can either create a new address using the GUI ("Receive" tab) or by using the command line (
getnewaddress)
