1) Is the Armory wallet the most secure, for online offline use (i dont care if the size is big or if its slow i care only about security)?
"Secure" is a very generic word. It really depends on what you are trying to protect against. Anything can be insecure if you use it incorrectly.
When used properly, Armory offline is probably one of the most secure wallets against malware or hackers gaining access to your private keys and stealing your bitcoins.
However, Armory puts the entire responsibility for recovery in your own hands. If you forget or lose your password, your bitcoins are gone forever. If you allow someone else to discover your password and allow them physical access to your Armory offline computer, they can steal your bitcoins. If you don't create a proper backup of your wallet and the Armory offline computer crashes (or is destroyed in a fire, tornado, flood, etc), then your bitcoins are gone forever. If you do create a backup, but you store it in the same location as your Armory offline computer and that location is destroyed ( in a fire, tornado, flood, etc), then your bitcoins are gone forever.
If you don't feel that you are capable of properly backing up your wallet and properly securing your password, then it might be more "secure" to use a service that can manage these things for you. Only you can make that decision.
2) Let's say I lose my wallet or accidentally delete it, or the USB that i hold them on gets stolen or lost, but i got the private keys on a paper, can the wallet be recovered?
Yes. As long as you have the correct private keys, the bitcoins can be recovered. If you don't fully understand how bitcoin works, then there is potential for you to not have all the private keys that you need. If the "USB that i hold them on gets stolen" and it isn't protected with a password (or the thief can figure out the password), then it is possible for the thief to steal the bitcoins before you can recover them.
3)If my wallet is stored offline, and i back it up like 5 times, but if someone sends me bitcoin, then those 5 wallets become obsolete, and don't work anymore?
No. The wallet only becomes obsolete when you use a new bitcoin address that hasn't been backed up. Some wallets will create new addresses without telling you. I don't think Armory does that, so as long as you don't import any private keys that were generated somewhere other than in the Armory wallet, you should be fine.
Or how does it syncronize with the network if new data comes in?
The first thing to understand is that there aren't any bitcoins in any wallets at all.
The only thing your wallet is storing is the private keys that allow you to create digital signatures to authorize the transfer of control of the value that is represented in the blockchain.
The blockchain is a public ledger that every full node on the network has a complete copy of. Transactions in that blockchain indicate how much value you can re-assign with signatures from your private keys. As long as you don't have any new addresses, you don't have any new private keys, and therefore the currently backed up private keys can still authorize the transfer of the new value that you received in the blockchain.
If I remember correctly, Armory uses deterministic private keys. Therefore, as long as you've backed up the wallet secret ID, and you haven't imported any private keys from anywhere else, you will always be able to re-generate all your private keys from that one seed. This means that even if you create new addresses (as long as they are created with the same Armory wallet), your original backup would still be able to restore access to the bitcoins sent to the new address.
4)I heard that you can transfer BTC in offline mode between wallets, how does that work if the BTC has to synchronize with the network?
You have to sign the transaction on the offline computer (in offline mode), then you need to transport that signed transaction to an inline computer to broadcast it to the network. It is also possible to export private keys from one wallet and import them into another wallet, but this destroys the ability to rely on the original backup since the wallet will then have a private key that was not generated from the original seed.
5)In Armory there are some standard private keys and compressed ones, what if a new version of the Core client comes out and the key format becomes obsolete, do i lose access to my BTC?
No. The transactions are already in the blockchain which require you to satisfy the existing script. The only way to change that requirement would be for you to spend that value and assign it the new requirement.
