Q1 : How do I see how many cabinets are networked?

"You can connect to up to ○ cabinets" is displayed on the Title Screen during Attract Mode. This "○ cabinets" shows the possible number of network connections. For example, if it doesn't show "You can connect to up to 4 cabinets" even though four cabinets are installed, then there is a possibility they aren't networked for some reason (such as the network cable being loose).

Q2 : There is something like a clock on the Title Screen. What's it used for?

This displays the internal clock. Use it as a reference when earning "Date Titles" that depend on the date.

Q3 : "Rev *.**" is displayed on the Title Screen, but what is it used for?

This displays the software version running on the machine.