Unless further restricted by your company documents (FOM/AOM, FHB/AFM), the 747 series (200/300/400 at least) are certified to autoland when coupled to any approved/certified ILS. It makes sense to alert Approach and/or Tower that you will autoland, so they can protect the ILS intrusion zones on the taxiways. If you don't, you may get undesirable excursions.
Generally 2 or 3 functioning and connected autopilots are required for a full autoland, just as they are required for Cat 2 and Cat 3 approaches.
So, to practice a Cat 2 or Cat 3 approach/landing, you can do it in any weather, as long as you meet the requirements and notify Approach/Tower.