How it works:
- Downgrades the game to version 1.0.0.0 using binary patches, leading to a (mostly, only difference is launcher and addition of xliveless and a commandline.txt file to allow the game to launch) perfectly replicated 1.0.0.0 version (this is mostly for my own convenience to only maintain one set of patch files, but also to give the user more options for which version to install)
- (if enabled) Install the selected patch by using Rockstar's official installer.

It supports installing all patches from 1.0.1.0 up to 1.0.8.0 (including the Russian and Japanese versions).

Before using this I recommend verifying your game files on Steam to make sure you have all the original files. The program automatically makes a copy of the game in case something goes wrong so you're not left with a non-functional GTA IV install.

My testing so far has not been super in-depth, so I'm releasing this as a beta. If any problems crop up, please let me know. 

GitHub repository with all the code involved: https://github.com/hoXyy/IVCE_Downgrader

* GTA IV: Complete Edition Downgrader (currently only for the Steam version)

1.0.4.0 Patch Installer

Splits from 1 to 200 for running All Pigeons.

200 splits

This split file goes with the starter guide/route. Only missions are included. Any additional information will have to be added by the user.

Any%

To help runners who are learning the game.

Any% splits with route for calls/texts

Archive containing 1.4 patch files

Archive containing RGSG

Classic splits, from back in the day

Classic World Record route splits

fonts.zip

This guide will help you learn everything you need to know about the phone calls and text messages in the game.

GTA IV Calls & Texts Guide

Use this chart to learn how dying affects the time of day.

GTA IV Dying and Time Change Chart

Use this chart to learn the friends' availability/unavailability hours.

GTA IV Friend Availability Chart

See this thread for more info: http://www.speedrun.com/gtaiv/thread/uftrz/1#fg9q4

GTA IV Game Flow Chart

Use this chart to learn how a pay 'n' spray affects the time of day.

GTA IV Pay 'n' Spray Chart

GTA IV Routing Documents

To install, you have to use Simple Native Trainer. Put objects.ini in game directory, then enter trainer menu and load objects from .ini. Some qubes are hidden underground. Second trigger is not a landing zone, you can land anywhere as long as you fly through both triggers. Examples: https://imgur.com/a/1i17owB

GTA IV Unique Stunt Jumps Trigger Zones

This chart shows every vehicle's top speed and compares Kyle's testing to gta4.net's testing.

GTA IV Vehicle Top Speed Chart

gtaForums' Savegame Catalog

Intermediate+ Mr. & Mrs. Bellic Time Setup

Most Wanted splits

A collection of saves after various missions all made by me. SoBoHoe is included.

My Google Drive with Any% practice saves

Radar Icons

Radio Downgrader

Rockstar Social Group Tool (RGSG)

Trainer

World Record Route segment saves

What you need to install xliveless. Read the readme file for instructions

xliveless

THIS GUIDE IS OUTDATED, BUT COULD BE USEFUL TO SOMEONE WITH A PHYSICAL COPY OF THE GAME. MOST OF YOU WILL WANT TO USE HOXI'S DOWNGRADER. IT'S AT THE TOP OF THIS PAGE.

[OUTDATED] How to Downgrade GTA IV to Version 1.4

Shadow_Dog

Powdinet

Kyle

hoxi

Kamiks0320

Sorviknight

doodooshower

goodron

Grand Theft Auto IV

North Alderney

QUB³D

Console

Platform

I remember many years ago viewing the beginning of a highlighted run which started just as the previous attempt was coming to a semi-disastrous close. Sometimes a VOD like this was accompanied by a remark signaling frustration or lost hope which, I suppose, the runner felt was a bit of amusing juxta

Name	Manager
* GTA IV: Complete Edition Downgrader (currently only for the Steam version) by hoxi	Kyle 1 year ago
GTA IV Calls & Texts Guide by Kyle	Kyle 8 years ago
GTA IV Dying and Time Change Chart by Kyle	Kyle 7 years ago
GTA IV Friend Availability Chart by Kyle	Kyle 6 years ago
GTA IV Game Flow Chart by Powdinet	Kyle 7 years ago
GTA IV Pay 'n' Spray Chart by Kyle	Kyle 6 years ago
GTA IV Routing Documents	Kyle 6 years ago
GTA IV Unique Stunt Jumps Trigger Zones	goodron 3 years ago
GTA IV Vehicle Top Speed Chart by Kyle	Kyle 8 years ago
Intermediate+ Mr. & Mrs. Bellic Time Setup by Shadow_Dog	Kyle 2 years ago

Name	Manager
200 splits by doodooshower	doodooshower 3 years ago
Any% by Kyle	Kyle 5 years ago
Any% splits with route for calls/texts by Sorviknight	Sorviknight 1 year ago
Classic splits, from back in the day by Kyle	Kyle 4 years ago
Classic World Record route splits by Sorviknight	Sorviknight 9 months ago
Most Wanted splits by Kyle	Kyle 3 years ago
Radar Icons	Kyle 6 years ago

Name	Manager
gtaForums' Savegame Catalog	Kyle 8 years ago
My Google Drive with Any% practice saves by Sorviknight	Sorviknight 3 months ago
World Record Route segment saves by Kamiks0320	Kamiks0320 2 years ago

Name	Manager
1.0.4.0 Patch Installer	Kyle 6 years ago
Archive containing 1.4 patch files	Kyle 7 years ago
Archive containing RGSG	Kyle 6 years ago
fonts.zip	Kyle 7 years ago
Radio Downgrader	hoxi 4 years ago
Rockstar Social Group Tool (RGSG)	Kyle 7 years ago
Trainer	Kyle 6 years ago
xliveless	Kyle 7 years ago
[OUTDATED] How to Downgrade GTA IV to Version 1.4 by Kyle	Kyle 6 years ago