The creator of an account automatically will be set as the recovery account, but this doesn't mean the new account is owned by the creator. That would mean sc01 and justyy own thousands of accounts, which is not true, of course. The recovery account does not necessarily have the private keys for the accounts he created. For recovering an account, the recovery account does not need to know the keys of the account to be recovered.

SC01 seems to be the recovery account for many accounts these days. Does this mean SC01 is farming?

No, as I explained above, sc01 just was the creator of the account (passively), which is the case when creating a new account via steemit.com nowadays. I guess the logic was changed to use sc01 instead of "steem" to easen the process of recovering an account without having access to the private active key of "steem".

I have more than one account and many old Steemians have that. I don't see any wrong in it, also not in helping others to start one.

Yes, there is nothing wrong with owning multiple accounts. Almost all witnesses have multiple accounts too. It sometimes also makes sense for security reasons to manage assets for a specific service in a different account.

Setting a new recovery is also an endless story or is it impossible?

It is possible, but it should only be done if the owner of the account knows what he is doing. For example, you should not set sc01 as recovery account for an account you yourself created, because the account recovery feature on steemit.com will not work/allow recovering an unknown account in most cases.