The EM4425 is a sophisticated chip with many NFC chip features and UHF RFID chip features. The EM4425 comes in several versions (V10..V12) which have different features and configurations; see the technical specification for the specific details. The EM4425V12 comes from the manufacturer in an uninitialized state, and must be initialized before any usage to configure the chip features to the user’s needs. The EM4425V10 is initialized by the manufacturer in a state optimized for NFC consumer engagement (mobile apps reading NDEF) and standard usage of UHF RFID.
Specialized software must be used to perform the initialization process of the EM4425 chip; not event EM’s own mobile apps or the NXP NFC TagInfo app work correctly with an uninitialized tag. Therefore it is recommended to use the EM4425V10 so that the initialization step does not need to be performed, unless there is a very specific use case requiring custom configuration.