Do MW2 Challenge Lobbies Give 10th Prestige on Xbox 360? No

No. Challenge lobbies (private matches with modified rules) do not grant Prestige progression.

Why

• Prestige = Public Match XP: Only earned in ranked public matchmaking (Team Deathmatch, Domination, etc.).
• Private Match XP Capped/Disabled: Custom games give minimal or zero XP toward rank/prestige.
• 10th Prestige Was Max: In MW2 (2009), 10th Prestige (Level 70 × 10) was the cap. No "Prestige Shop" or rewards beyond emblem/calling card.
• Modded Lobbies Risk Ban: "Infection" lobbies (hacked XP, god mode) trigger anti-cheat; console/account bans were common.

To reach 10th Prestige legitimately: play public matches, complete challenges, use XP bonuses (double XP weekends). It takes ~30–50 hours.