Hi people!!

I recently purchased a Trezor to use it as a secure vault for my small BTC, and it's an amazing device: very high secure, U2F compliance, some good apps for everyday usage (also thinking about buying another one (new model?) for backup purposes, but I have 2 questions I cannot answer. Perhaps they're answered in another posts, but I couldn't find them (sorry if that's so):

a) what may happen if the domain mytrezor.com is down because SatoshiLabs crashes? I couldn't have access to the device to use my private keys to make online transactions. Is there any option to download source code and create a webserver using localhost and a specific /etc/hosts entry?

b) when using hidden wallets, how is the passphrase generated within the device when multiple wallets are used? Is the seed related in this process? Because if I use the seed to recover my wallets, the passphrase couldn't be generated unless you put it explicitly, so it'll be impossible to access my wallets If I only know the seed, therefore all my BTC will be lost, aren't they?

Thanks for your help ;-)