回答:
Please note, this FAQ contain mild spoilers.
Outfits (Altair Robe / Armour of Brutus / Turkish Armour)
Available at the start of Sequence 2.
1. Access the in-game Pause Menu and select Inventory.

2. Select Outfits.

3. Your outfits will be unlocked here.

Vlad the Impaler Single Player Mission
Available at Sequence 3/Memory 10.
1. Access the in game map by pressing Select and locate the Hidden Tomb.

2. Once inside the hidden tomb, you will locate and interact with a book that will unlock a second hidden tomb.


3. Locate and run to the second hidden tomb to access the mission.


Ammo Capacity Upgrade (Raises bullet quantity from 10 to 12)
Available at the start of Sequence 2.
1. Access the in-game pause menu and select Inventory

2. Select Supplies

3. Select Bullets

The Lost Archive
Available from the main menu screen as shown in the image below:
Outfits (Altair Robe / Armour of Brutus / Turkish Armour)
Available at the start of Sequence 2.
1. Access the in-game Pause Menu and select Inventory.

2. Select Outfits.

3. Your outfits will be unlocked here.

Vlad the Impaler Single Player Mission
Available at Sequence 3/Memory 10.
1. Access the in game map by pressing Select and locate the Hidden Tomb.

2. Once inside the hidden tomb, you will locate and interact with a book that will unlock a second hidden tomb.


3. Locate and run to the second hidden tomb to access the mission.


Ammo Capacity Upgrade (Raises bullet quantity from 10 to 12)
Available at the start of Sequence 2.
1. Access the in-game pause menu and select Inventory

2. Select Supplies

3. Select Bullets

The Lost Archive
Available from the main menu screen as shown in the image below: