"1257" represents a snapshot in time where the developers won. It signifies a working exploit or a valid signing method. However, in the iOS world, these victories are fleeting. A build verified today might be revoked by tomorrow, sending users back to the search bars looking for the next iteration (perhaps "1258" or "1300").
If you cannot find YouTube in the App Store, it is likely because the current version is incompatible with your device. You can still download the last compatible version by following these steps: Use Purchased History: Instead of searching the store, go to App Store > Updates > Purchased Cloud Icon: youtube download ios 1257 verified
May break every few weeks. Requires manual re-installation of the shortcut. "1257" represents a snapshot in time where the