Because these files are parts of a single larger archive, you cannot "use" Part 2 on its own. To extract and play the game, you need to follow these standard steps for multi-part RAR files: How to use Part 2
: Unlike the main EDF series, Iron Rain was developed by Yuke's and features a more "westernized" aesthetic with character customization and a "Prowl Rider" class that lets you ride giant insects. EARTH.DEFENSE.FORCE.IRON.RAIN-CODEX.part2.rar
: It takes roughly 12 to 13 hours to complete the main story. Because these files are parts of a single
: The game features 52 missions in its main campaign. EARTH.DEFENSE.FORCE.IRON.RAIN-CODEX.part2.rar
If you are looking for a "good piece" of advice or information regarding the game itself: