These are my saves that I made while getting 100% of the achievements. All obtained without using cheats.

Save link: https://drive.google.com/file/d/1DCXSUfEFFW5sl3j0QPrBhUrYMzDcmLnh/view?usp=drive_link
How to replace the file below

Achievements that can be obtained with it:

Not So Fast
Complete The Exchange


Is That All You've Got?
Achieve 100% completion


King of Liberty City
Unlock all achievements
Note:If you taken all other achievements

What to do: Start the last mission. After the scene with the helicopter, go back at the home, there are all the necessary weapons. The problem should not have arisen at all

Save link: https://drive.google.com/file/d/1gnTS6CNW-iaMWKPMKAPNOd4FI_4KyNhv/view?usp=drive_link
How to replace the file below

Achievements that can be obtained with it:

If You Ain’t Cheatin’, You Ain’t Tryin’
Blow up 2,000 cars
Note: Blow up one car. This RockStar launcher only achievement

Wheels Up
Complete 20 unique jumps
Note: Complete last one at the airport


Where we’re going, we don’t need roads
Complete 4 off-road missions: Patriot Playground, A Ride in the Park, Multi-Story Mayhem and Gripped!
Note: Complete last one at the last island. This RockStar launcher only achievement



Blood in the Streets
Pass all 20 Rampages
Note: Complete last one at the last island. This RockStar launcher only achievement


Play Fetch
Complete the Portland Docks and Shoreside Vale import/export car lists
Note: The last car Cheetah in the garage on the third island. This RockStar launcher only achievement

Liberty City Secrets
Collect 100 hidden packages
Note: Take last one on the third island


Talks a Lot
Complete all phone missions
Note: Complete last one naer home. This RockStar launcher only achievement


Man Toyz
Complete every RC Toyz mission
Note: Take last one on the firs island


Furious First Responder
Complete Paramedic, Firefighter, Vigilante
Note: Put out one fire on the third island

Pest Control
Deliver all emergency vehicles to the crane at the Portland Docks
Note: Deliver the tank from the garage on the third or second island. This RockStar launcher only achievement

Where To?
Complete 100 taxi fares
Note: Complete last one. I'm not sure it will work

1. Download the save you are interested in from the link
   
2. Make sure the game is not running. Even being in the start menu blocked the file update for me
   
3. Open the folder with saves
   Way: C:\Users\{UserName}\Documents\Rockstar Games\GTA III Definitive Edition\Profiles\{UserID}
   
4. Replace the current save file with the downloaded one
   WARNING:The files will replace slots 1 and 2 respectively. Make sure you don't lose your save and make a backup. If you want to change the save slot for the downloaded file, change the last digit from 1 to 8. 9 - autosave

Thank you for your rating!

Spent a gigantic amount of time preparing these saves. Hope it helped you get 100% achievements. Happiness and good luck

Interactive map with all objects:
https://mapgenie.io/grand-theft-auto-3/maps/liberty-city

Site for checking the task list for 100%. You can see the required collectibles on the map. Works for all three parts of the Definitive Edition
https://gtasnp.com/