Cheats are not available in v1.11 and higher.
Access the cheats by editing the desktop shortcut. Right-click on the desktop Icon and go to "Properties", then in the "Target Field" edit the command lines so it reads:
C:\program files\eagames\moh_spearhead.exe"+set developer 1 +set ui_console 1 +set cheats 1 +set thereisnomonkey 1 +set cl_playintro 0
Click "Apply" and then "Ok". During game-play press "~" to display the console window and then enter the following cheats
God mode: dog

Full health: fullheal -or- fullheald
All Weapons and Ammo: wuss

Invisible: notarget
Third Person view: cg_3rd_person

Teleport to Location: tele

Display Coordinates: coord

Suicide: kill

List Models for Allies: playermodel
List Inventory: listinventory
List Maps: maplist
Set Walking Speed: set sv_walkspeed

Set Gravity: set sv_gravity
Set Health: health
No Clipping: noclip
Level Select: map

Level Completed: fadeout

Restart Level: restart

Unlock Mission 2: seta g_m2l1 "1"

Unlock Mission 3: seta g_m3l1 "1"

Unlock Mission 4: seta g_m4l1 "1"

Unlock Mission 5: seta g_m5l1 "1"

Unlock Mission 6: seta g_m6l1 "1"