Every Pokémon gets at least one new move on evolution (every version except v1.0.2)
As of v1.1.0, this is handled by a randomizer setting.
In-game option for instant text (v1.0.2+)
Attempting to select the instant text option in the randomizer will cause the game to crash. This is an intentional measure to stop IronMON players from trying to use settings files from the core Tracker rather than the ones designed for Nat. Dex.
Move and ability names are modernized. (v1.0.2+)
Ability pop-ups in battle à la Black/White. (v1.1.0+)
Moon Stones can be sold (v1.1.0+)
Super Kaizo mode (v1.1.3+)
At the start of the game, Mom will prompt you to enable it optionally.
All trainers have Smart AI
Hidden item events and sparkles are deactivated, excluding the ones in dungeons (except renewable hidden items) and the ones before Roxanne (Emerald) and Mt. Moon (FireRed)
Seashore House (Emerald) and every room on the S.S. Anne with Trainers (FireRed) are blocked off.
(FireRed) Route 25 and Route 24 post Nugget Bridge are blocked off until the player has received the Cascade Badge
(FireRed) Celadon Game Corner is blocked off until the player has received the Rainbow Badge
Emerald
Diving speed is doubled
Item balls containing TMs appear green
All Pokémon Centers have a Name Rater
They are represented by a sprite of Dusclops
PC Potion was moved next to the Starter bag
The player will receive both the Mach and Acro Bike at once
An NPC in Oldale Town was modified to max out your Pokémon's friendship. It can only be used once per save file.
Please note that this is against the spirit of IronMON and should only be used if you are fully aware of it.
There is a Nurse stationed in Petalburg Woods. She will only heal your party if none of your Pokémon are poisoned.
Despite the removal and/or truncation of most cutscenes, you will not be warped to the Lab after the first rival battle if you win while poisoned.
FireRed
Item balls containing TMs appear yellow
All Pokémon Centers have a Name Rater
They are represented by a sprite of Slowbro
PC Potion was moved to Oak's Lab
Hidden items that have a chance to respawn after 1500 steps are now guaranteed and don't respawn, except in Mt. Moon
Bill no longer asks you to go to the Sevii Islands after defeating Blaine, but you can still see him in Cinnabar's Pokémon Center
An NPC in Viridian City was modified to max out your Pokémon's friendship. It can only be used once per save file.
Please note that this is against the spirit of IronMON and should only be used if you are fully aware of it.
There is a Nurse stationed in Viridian Forest. She will only heal your party if none of your Pokémon are poisoned.
The Move Reminder, located initially on Two Island, has moved to Celadon City. His house is west of the Pokémon Center.
You couldn't enter this building in vanilla
A Hiker NPC outside Rock Tunnel will give out HM05 Flash.
Purchasing 10 Poké Balls at once will give you a free Premier Ball, à la Pokémon Emerald. (v1.1.1+)
Randomizer
The randomizer will natively scale the levels up to as high as 60%
The "Legendary" ban list now contains all Pokémon with 600 or more BST, excluding sub-600 BST Legendary and Mythical Pokémon. Meanwhile, the "Strong Legendary" ban list is the same, but without any non-Legendary, non-Mythical, or Pokémon with exactly 600 BST.
The 600+ BST ban list changes to a 641+ BST ban list when "Randomize OTs" under the in-game trade section is unchecked. (v1.1.0+)