LAND2/3 is displayed after the autopilot confidence check when the second autopilot engages. Around 1200ft AGL. Yup, a rudder channel is required as CAT IIIb requires automatic rollout (yes, a HUGS would be ok as well, we don't have that).
Yup, there is CAT I reversal with a NO AUTOLAND message, if above the minimum simply switch the minimum selector to BARO and continue to the CAT I minimum. We usually (not SOP, but suggested technique) set the CAT I minimum on the BARO scale, then switch it over to RADIO and dial it down to nothing. That way we still get a triangle at the CAT I minimum, which is usually at 200ft AGL where the land/go around decision has to be done as it is the alert height. If below the minimum it is a mandatory go around of course. Personally i would rather go around if something like that happens below 1000ft AGL and sort it out afterwards.
Press the additional cancel/recall button on the MFD panel above the upper DU which displays any autoflight failure messages on the upper DU. It is installed below the SYS button. Has to be checked whenever a checklist calls for a recall check. Usually additionally pressed during the approach briefing to make sure that the required mode is available.