In the official version of HITMAN 3 (now part of World of Assassination), playing offline severely restricts your access to unlockable content because progression is tied to the game's "always-online" servers. However, players can bypass these restrictions using third-party mods or specific server emulators. Official Offline vs. Online Capabilities

Conclusion

This method manually triggers the "unlocked" flag for weapons like the Krugermeier 2-2 Silver, the Sieger 300 Ghost, and various remote explosives. The Offline Experience Tool (The Peacock Project)

2. Modding (PC only)

On PC, there are mods (e.g., on Nexus Mods) that claim to unlock all items, including for offline use. These often require replacing game files.
Warning:

Hitman 3 is a phenomenal sandbox. With everything unlocked offline, it becomes the ultimate stealth playground—no FOMO, no grind, just pure assassination.