>Talking about opening the enclosure, is it the SOM enclosure or something else ?
No, your enclosure - the enclosure you will put your product in. if you have this feature enabled and GPIO assigned to it, then the system will get notified if the enclosure is or was open via GPIO/interrupt
>The existing digital and analog interfaces use MCA pins. Does it mean that the tamper events detector pins are already connected to the encoluse of the SOM ?
See above - some does not have any enclosure. You build your product, create an enclosure and connect pins to it.
>Or need physically to connect them to the enclosure we want to protect ?