If you bought GTA IV on Steam today, you have version 1.0.8.0. You cannot directly download 1.0.4.0, but you can downgrade it.
To play on 1.0.4.0, you generally have two options:
Before you attempt to downgrade, be aware of the downsides:
Proceed with a downgrader tool if you own the Steam version. Avoid standalone executable downloads from untrusted websites.
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