If you download a random code_pre_gfx_mp.ff from a sketchy forum post from 2012, you are almost guaranteed to get the "File different from server" error again. There are dozens of versions of this file (Steam, retail disc, IW4x, v1.0, v1.13, etc.).
A: No. Single player uses code_pre_gfx.ff (without _mp ). Do not rename the multiplayer file; it will crash the campaign. Code-pre-gfx-mp.ff Download Modern Warfare 2
Introduction: The Gatekeeper File of Modern Warfare 2 If you download a random code_pre_gfx_mp