Intercom Central 413 - Three Channels HOME Power-line Intercom System, 3 Wire, White, Two Stations Set

So it doesn't matter if the locations are on different breakers as long as they run to the same fuse box on the same meter?

Will the lock button stay on these intercoms without automatically shutting off?

Will this system work between main floor and basement?

Is this for only two rooms or three rooms?