Here are differences between the rushed early US release of Ico (PS2 - NTSC-U/C) compared to all other versions, which are basically the same (PS3, PS2 NTSC-J, PS2 PAL 60hz) except for the glitch jump (PAL 50hz).
Some differences are aesthetic and are not listed here, a couple are actually helpful, but most impact the runtime negatively:
--PUZZLES--
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No drawbridge forces you to take Yorda on the Trolley and Crane
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No water pump or watermill puzzles in the waterfall section, they are flat out just missing. This actually makes these puzzle areas take more time, because the unfinished solutions are slower.
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All other puzzles and mini-skips are possible and solved the same way as PS3/PS2-J runs.
--SHADOWS--
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Shadows all have higher HP (14 hit points, while in PS3/PS2J/PAL smaller shadows have 7, larger have 11).
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Shadows are more aggressive and also more difficult to deal with. They are better at dodging, team up on you more, will hit through your swings (while other versions make that a tie and Ico and shadows just block each other to no dmg), and take Yorda to pools faster when in the air.
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First shadow is SO fast (you almost can't save Yorda from getting put in pool) and has 8 hp instead of 4.
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Spider shadows can hit you in this version, WHAT THE WHAT?!?
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Shadows at the water tower WILL follow Yorda onto the block that hangs from the chain. In other versions, the usually just watch from the ledge.
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Final shadow fight takes longer because many shadows will just swirl in circles instead of coming towards you. You have to hunt them down and then still chase them. They swirl around stone Yorda, the right first ledge, the left back of the room towards the stairs, and possibly one or two other places.
--CUTSCENES--
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LOTS more unskipable cutscenes than in PS3/PS2japanese versions, making the runtime longer. Skipable cutscenes include Yorda leaving her cage, first main gate cutscene, and the water tower explosion for some weird reason. All other cutscenes cannot be skipped once they begin.
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several shadow fights are now unskippable because you can't skip the cutscenes during which they spawn and move towards Ico and Yorda (example: E.Idol Stairs skip), while other's take more time to set up so Yorda is at a safe distance (example: W.Idol Stairs).
--MECHANICS--
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Calling Yorda swings the camera HARD, making this an unusable strategy to run faster in much of the game.
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Dropping from chains does not auto catch (so you die if you drop from the top of the crane, for instance)
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Ico climbs up ledges both with the TRIANGLE and with pushing UP. In other versions, it's only the triangle. This makes it very easy to accidentally climb when not wanting to.
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Yorda does NOT shake her head at you EVER... so yay?
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Holding Yorda's hand is by tapping R1 rather than holding it down, same to let go (other versions make this mode an option but it is not the default).
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Yorda holds Ico's hand much better... let's go less often at corners or when he is swinging the stick while holding her hand.
--OTHER--
- No IGT is displayed when beating the game because there is no final save option
- No NG+ mode (2 player, lightsaber, melon), removing this as a possible speedrun sub-category
NOTE: Besides the above differences, many of the jumps and movement tricks still work, although the 4:3 aspect ratio changes some of the visual cues. Thus, the PS3 speedrun tutorial videos are still helpful. Also, gooperman recently got the WR in the NTSC-U category and SanchoPanda did an analysis of his run. If you are considering running this version of the game, this video is highly recommended: