56K ITU V.92 ready Fax/Modem (RJ-11 port)

If the specification for the modem of a computer is as above, can I use cable connection? Is there any need to change / add extra hardware, apart from the modem box from the cable company?

N0 - that modem only works with analog phone lines

The Cable modem either requires an ethernet connection (RJ-45) or a USB connection. The latter is only recommended for a single user.

The cable modem must be before any amplifiers of the amps in the coax must be bi-directional.

Modems mix a lot of stuff together. They can be routers, wireless routers and switches.

If your only connecting one computer, you may or may not need a crossover Ethernet cable. This depends on your computer and cable modem model.

It must be a modem to demodulate the cable signals. It usually is a router to be able to route signals.

It MAY contain a switch, hub or a wireless access point.

As noted, the modem you refer to is an analog modem for use connecting via phone lines.

If your computer is not ancient, it will probably have an ethernet port. It will look like a larger version of the jack on the modem.

If you subscribe to a cable service, they will usually provide the cable modem.