Pokemon Fire Red Essence

The goal of this ROM hack is to retain the essence of the original game while allowing you to catch all of the Pokémon that were supposed to be caught in Fire Red/Leaf Green. All Pokémon can be found where they normally are, eliminating the need to consult a README file to determine their location. This hack is not for you if you want to catch all 386 Pokémon. If you want to be able to catch every Pokémon in Fire Red, regardless of version exclusivity or trading requirements, then this hack is for you!
Features

The changes can be divided into 3 groups; changes that allow for the completion of the Kanto Dex, changes that allow non-Kanto Pokémon to be caught, and quality-of-life changes and modernizations.
Changes that allow for the completion of the Kanto Dex

1. Fire Red/Leaf Green exclusives present in all areas

For example: in Fire Red, Ekans is present in route 4. In Leaf Green, Sandshrew is present in route 4. In Fire Red Essence, Both Ekans and Sandshrew are present in route 4. This is true for every area in the game.

2. Pokémon that normally evolve by trading now evolve at level 37

For example: Graveler, Machoke, Haunter, and Kadabra.

3. NPCs on Six Island will give you the fossil and fighting Pokémon you did not pick

If you chose Omanyte, an NPC will give you Kabuto, and vice versa. If you chose Hitmonlee, an NPC will give you Hitmonchan, and vice versa.

4. Pinsir is now available as a prize at the game corner

Pinsir was available in Leaf Green, so it’s only fair that he is available in this hack too. A level 25 Pinsir is available for 5,500 coins. This option replaces Clefairy as a prize Pokémon.

5. The starters you did not pick can be found in Rocket Warehouse

There will be two Pokéballs in the final room of Rocket Warehouse on Five Island containing the two starter Pokémon you did not pick.

6. An NPC on Seven Island will reward you for completing the Kanto Dex

If you complete the Kanto Dex and receive your Diploma from Celadon City, you will receive Mew as a reward.

Changes that allow non-Kanto Pokémon to be caught

7. An NPC on Seven Island will give you the Mystic and Aurora Tickets

This will allow you to travel to Navel Rock and Birth Island to catch Ho-Oh, Lugia, and Deoxys.

8. Entei, Suicune, and Raikou no longer roam and can now be found at Navel Rock

In the original game, only one legendary dog was available depending on your starter choice, and it would roam Kanto until you found it. They suffered from two glitches: they always had bad IVs, and if Raikou or Entei used Roar they would be gone from the game forever. Now all three Johto legendaries are available and can be found in Navel Rock.

9. Cut content from Altering Cave has been added

The Altering Cave was originally supposed to contain various Johto Pokémon that would alternate based on a mystery gift. This never made it into the final game and instead, the cave had nothing but Zubats. Now, the cave contains all the Johto Pokémon that would have been available to catch. These Pokémon are: Mareep, Aipom, Pineco, Shuckle, Teddiursa, Houndour, Stantler, and Smeargle.

10. UP-GRADE, Metal Coat, Dragon Scale, and King’s Rock are no longer held items

They are now single-use items used to evolve Porygon, Scyther, Onix, Seadra, Poliwhirl, and Slowpoke. They are still found in the same locations and are still the rewards for completing the Trainer Tower.

Quality of life changes and modernizations

11. TMs are reusable

Just like in later Pokémon games, you are free to use TMs as many times as you want.

12. HMs are now forgettable

Now HMs can easily be replaced by other moves.

13. The running shoes are available from the beginning of the game and you can run indoors

This makes the beginning of the game less tedious and makes the later game more convenient when indoors.

14. Stats that are affected by natures are color-coded on the summary screen

Just like in later Pokémon games, the increased stat will be red while the decreased stat will be blue.

15. Flame body and Magma armor now cut the steps needed to hatch an egg in half

Just like in later Pokémon games, this makes egg hatching much less tedious.

16. Move tutors are reusable (Except for the one in Cape Brink)

Move tutors can now be used as many times as you want, except for the move tutor that teaches the ultimate move to your starter in Cape Brink.

17. The Move Reminder no longer requires mushrooms

The Move Reminder on Two Island will now help you relearn moves for free.

18. Adjusted game corner coin rate

Instead of paying $1,000 for 50 coins and $10,000 for 500 coins, you now pay $1,000 for 500 coins and $10,000 for 5,000 coins. This makes getting Porygon and some essential TMs much less tedious.

19. Moon stones are now sold in Celedon Department Store, Sun Stones are now sold in Seven Island Mart

This makes it so Moon stones and Sun stones are no longer finite items.

20. The Silk Scarf and Dragon Fang can be bought from the game corner

The Silk Scarf replaces the Smoke Ball and the Dragon Fang replaces the Yellow Flute.

21. Minor dialogue alterations to be consistent with changes

For example: Brock now says that TMs have infinite uses instead of saying they can only be used once.