Bring down the console in game with your tilde key (~) and enter the following to play your desired mission. This will allow you to play missions you are yet to unlock.

Cheat - Effect

map rhine - Play "The Crossing Point"
map cityhall - Play "Stalingrad City Hall"
map downtown_sniper - Play "Comrade Sniper"
map libya - Play "Crusader Charge"
map 88ridge - Play "88 Ridge"
map toujane_ride - Play "Armoured Car Escape"
map toujane - Play "Retaking Toujane"
map matmata - Play "Assault On Matmata"
map duhoc_assault - Play "The Battle Of Pointe Du Hoc"
map duhoc_defend - Play "Defending The Pointe"
map silotown - Play "The Silo"
map beltot - Play "Prisoners Of War"
map crossroads - Play "The Crossroads"
map hill400_defend - Play "The Battle For Hill 400"
map hill400_assault - Play "Rangers Lead The Way"
map bergstein - Play "Bergstein"
map breakout - Play "The Brigade Box"
map newvillers - Play "The Tiger"
map downtown_assault - Play "Downtown Assault"
map trainyard - Play "Railroad Station No. 1"
map tankhunt - Play "Repairing The Wire"
map eldaba - Play "The End Of The Beginning"
map elalamein - Play "El Alamein"
map decoytown - Play "Holding The Line"
map decoytrenches - Play "The Diversionary Raid"
map demolition - Play "Demolition"
map moscow - Play "Red Army Training"