Metamaska Keys Security Practice and Theory - private keys generation mechanism

When Metamask account is created its give us a seed with words- it also creates first address with private key.

For every new key we keep same seed phase to metmask account so if we uninstall the metamask and will put the seeds in to newly installed metamask we will recover first account and then each new one will be same as on old account.

Now the main point :

1- Is this mean that if someone got the key to first account he can get access to all other accounts without knowing the seed phase ?

2 - If someone got the key to account number 3 for example - can he gain access to accounts 4, 5, 6 and so on to any account created after account 3 ?

3- If Someone has the key to account 3 - can he gain access to account 2 and 1 without knowing seed phase ?

Thanks for the answers in advance.

(post has been removed my mods in r/metamask so hopefully someone here can explain)