1. Can't the thief just try to unlock it by "bruteforcing" the pincode?
Not really. There's a delay between PIN entries which means that a brute force will take a significant amount of time. Furthermore, you can use the passphrases option to further hide your coins; without the correct passphrase, the correct private keys cannot be derived.
2. If I restore my btc on a new nano ledger s, how does it know all the receiving addresses by just having the word seed?
If I understand correctly the nano ledger s will use a different receiving address for every incoming bitcoin transaction.
So it has to have a way to know about all those addresses somehow, but how?
The mnemonic follows the BIP 39 specification to encode a seed value. That seed value uses BIP 32 to derive all of the private keys used by your wallet. Thus the seed holds all of the information that is necessary to reconstruct the private keys for your wallet.
Does it rely on any manufactureres service for keeping track on this?
No.
3. What if this happens in say 10 years.. Let's assume the nano ledger S devices are not available anymore and the manufacturere went bankrupt -> No support.
Can I still recover my btc without a nano ledger s device somehow??
Yes. You just need any wallet software that follows the BIP 39 and BIP 32 specifications. These are publicly documented and well specified. Even if such software does not exist, you could write or hire someone to write software that follows the specs.
4. Can the nano ledger S be used with anything else than chrome apps? It sounds like a broken solution to only have apps that rely on google chrome.
Isn't there any application that can use it natively?
Yes. any wallet software which supports the Ledger Nano S can be used. libraries for interacting with it are publicly available so wallet software can just use those. An example of one is Electrum.
