The world's first ever look at Grand Theft Auto III, a (presumably) December 2000 build shown in the January 2001 issue of PlayStation 2 Official Magazine-UK; these builds show a very different-looking game, alongside mentions of cut features.
There are a few things to note from the text in the magazine:
Pedestrians originally once walked their dogs. Animals would not appear all the way until Grand Theft Auto V.
Time originally ran on a 30-minute cycle, while the final game runs on a 24-minute cycle, where one minute represented one hour in the final.
There is mention of a ferry that allowed the player to travel between islands, which was seen in a conceptual map. It was later revived for Liberty City Stories.
Apparently, there was once a button that allowed the player to insult pedestrians. It was likely reworked into one of Claude's flipping the bird animation when he gets close to a car in the final.
Characters from the first game, second game, and London 1969 were meant to return, further tying into the 2D universe games, but none of them made an appearance.
An image of the HUD; according to the magazine, from A to F, it would've displayed your wanted level, cash, time, weapons, health and radar. The image would be publicly released online in the February 2001 prerelease.
Liberty Tree Preview
Grand Theft Auto III was unveiled for the first time on the internet on February 19, 2001, rather than via magazine previews.
At 0:27, the voice clip "Get out of the car!" can be heard, which is actually taken from Grand Theft Auto 2. It was once theorized that Claude talked in early builds, but in the 10th Anniversary Q&A, Rockstar responded with that they had no plans to implement a talking protagonist until Vice City. It's also likely that the voice clip was added in for effect.
Rockstar Games opened up a mock website of Capital Autos in order to promote the game. It contains some interesting and early car renders!
Grand Theft Auto III was shown off at E3 2001.
During Rockstar Games' Q&A from fans during the game's tenth anniversary, a excerpt of the early Grand Theft Auto III script was posted in comparison to the Grand Theft Auto IV script.
Intro A: Betrayal (A)
PLAYER gang burst out into alleyway from a bank job. Two of the gang run off, the PLAYER stays to let off both barrels to dissuade any hero's. PLAYER runs off after his gang members, he rounds the corner to find CATALINA standing over the body of the other.
Sorry babe. I'm an ambitious girl and you, you're just small time... (resounding ?????)
CATALINA then shoots the PLAYER twice. She grabs the case and then stands over the dying PLAYER. Just then MIGUEL pulls up in a sports car.
Catalina! Move your ass!
CATALINA runs over and hops into the car as it pulls away.
Intro B: Jail Break (A)
8 BALL and PLAYER bust out on the bridge. 8 BALL nails the guard with a huge punch.
God Damn that hurt! Alright, we've got no time to waste, let's get the hell out here!
Give Me Liberty (D) @ Luigi's Club
Having just escaped 8 BALL and PLAYER are looking for refuge. 8 BALL is quite anxious to get some shelter.
I know a place on the edge of the Red Light District where we can lay low but my hands are badly burned so you'll have to drive.
This is the place! Let's get off the street and find a change of clothes!
They approach the hide out.
I know a guy, he's connected. Name's Luigi. Me an' him go back so I can probably get you some work. C'mon, let's drop by and I'll introduce you.
Game On Exhibition
At the Game On Event in 2009, held in Taiwan, the mission drafts of Grand Theft Auto III were shown, persumably from a near-final build.
Some of the mission names are different;
Lips Forelli's Last Lunch
Mike Lips' Last Lunch
Kill Chunky Lee Long
Farewell 'Chunky' Lee Chong
The Bank Job
Take Out The Laundry
Taking Out The Laundry
Salvetore's Called a Meeting
Ice Cream You Scream
I Scream, You Scream
(Crossed Out Name)/Disco Inferno
Trial By Fire
Bomb Da Base
Bomb Da Base Act I
Big Day For Ray
Payday For Ray
Gone in 60
Grand Theft Auto
The Hand-over & The SAM
Plane to Sea
The El Burro Phone missions were originally able to be repeatable rather than classified as completed.
Paparazzi Purge came before Under Surveillance.
Marty Chonks' missions weren't present.
Bradygames Strategy Guide
PS World Footage
On the PS World Volume 12, Grand Theft Auto III was covered. Despite the disc being released in December, the differences date the build to around August 2001.
The logo was orange.
The color of the weapons HUD is a bright yellow instead of a dull gray, which would end up being used in the Windows version of the game.
The sniper crosshair was different.
Pedestrians' limbs could be shot off unlike the final.
Covered in PlayZone November 2001.
The game almost plays exactly like the final, except with some aesthetical differences;
The HUD matches that of the final game.
This build marks the last appearance of the blue Police cars.
This is the last appearance of the Bobcat with the cushioned trunk.
The game had several changes after the September 11th attacks in order to prevent comparisons to both it and New York; this included the LCPD cars having their NYPD-inspired blue/white design being changed to black/white, the removal of a mission with the word 'terrorist', altering plane paths so that they wouldn't appear to fly into and/or behind skyscrapers, and some pedestrian and radio dialogue being removed.
Interestingly, an earlier European version was seemingly released on accident, and is dated September 15, two weeks before the later European version; this release was likely an accident, given it lacks some of the censorship later versions have.