Remember, it's in Korean. Assuming you can read Korean (or just want to see the pictures), it's here.
He posts a new post there with every page, giving some commentary. He's also given a lot of information about the tower's world.
Luckily, fans have translated it here. Another collection of translations is here.
Translations for the individual after-chapter translations can be found on Batoto's forums, eg. here is the one for Season 2 Chapter 13. Though I think the people translating the comic itself now put those blogs after every chapter.
Technically, IIRC, the contract for an item is made when the item is created, and the item will only work on floors that its contract covers. I'm pretty sure that's what they said during Baam's Shinsoo lessons, anyway.
Likewise, the Great Families still require contracts, but they have a sort of "group contract" that covers the entire family -- that's why Laure was able to use Shinsoo to attack in the Crown Game, before anyone had made any contracts.
Irregulars, of course, are different, and have an unknown ability to (sometimes) manipulate Shinsoo without a contract. But as far as we know, they're the only ones who can do so (aside from, I guess, the Guardians, who presumably don't have to make contracts with themselves.)