Unlimited Ammo:
If you want the option to have unlimited ammunition for your weapons, you must first beat each mission on Hard Mode, finishing each with an S-Ranking.

Acquire New Scenarios:
Beginnings (I) – Pass “Train Derailment 3″
Beginnings (II) – Pass “Beginnings (I)” with at least an A rank
Dark Legacy (I) – Pass “Fall of Umbrella 3″
Dark Legacy (II) – Pass “Death’s Door” and “Nightmare (II)”
Death’s Door – Pass “Raccoon’s Destruction 3″ with at least an A rank
Fourth Survivor – Pass “Dark Legacy (II)”
Nightmare (I) – Pass “Mansion Incident 1″
Nightmare (II) – Pass “Nightmare (I)” with at least an A rank
Rebirth (I) – Pass “Mansion Incident 3″
Rebirth (II) – Pass “Rebirth (I)”
The 4th Survivor – Pass “Dark Legacy (II)”