Will aluminum #2 wire work with a 120 amp circuit breaker?

First off, assuming this in USA, 120 amp is not a standard overcurrent rating device setting.

Second, to determine the amperage rating of a conductor, need to know the insulation type.

I am sure there are other issues and question, let's go with the two I mention and we can go from there.

Yes it will "work" but is not rated for 120 AMPS. Aluminum #2, 90 degreeC, as service feeder is rated at 100 Amps

Aluminum #2, 90 degreeC, as service feeder is rated at 100 AmpsWe would never use the 90 deg C column in figuring real circuit amps, but regardless of temperature, #2AL is rated for a 100A dwelling service.

Novices reading the Code can be dangerous.

The 90 degree C column of Table 310.16 is off limits to anyone that has not been trained to use the Code.

This rating is only allowed to be used to rate ampacity if wire when the terminations are rated 90 degree C.

This rating of terminals and connections is very rare. Only seen in high usage and industrial equipment, and usually special order.