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MGS4 - Big Boss Hard - New Game Plus
Act 1
Red Zone NW Sector
Red Zone
Militia Safe House
Urban Ruins
Downtown
Advent Palace
Advent Palace (Frogs)
Crescent Meridian
Millennium Park
Act 2
Cove Valley Village
Power Station
Confinement Facility
Vista Mansion
Research Lab Facility
Mountain Trail
Mountain Trail Riverside
Drebin's APC
Marketplace
Act 3
Midtown S Sector
Midtown NE Sector
Midtown N Sector
Church Courtyard
Echo's Beacon
Act 4
Heliport
Snowfield + Heliport
Tank Hangar + Canyon
Nuclear Warhead Storage Bldg 1F + B2
Nuclear Warhead Storage Bldg 1F
Snowfield & Communications Tower
You can be more aggressive on the lower difficulties and take the alert/damage from the frogs. It turns into a high risk, high reward, since Wolf will see you as well. On Liquid Easy she will always spawn behind the wall (@2:08 mark on the video).
Blast Furnace
Casting Facility South
Casting Facility North
Underground Base
Underground Supply Tunnel
Surface Tunnel
Port Area
Act 5
Ship Bow
Command Center
The frog skip before the Mantis fight will not work on Liquid Easy since the frogs are instantly knocked out with a tranq. All other difficulties will be the same.