For those who don't know, the Mystery Dungeon games play a bit... differently compared to the main series. The most noticeable differences are:
The dungeons that are explored are randomly generated, meaning that the dungeon won't ever be the same experience twice
Effort Values and Individual Values are not a part of this game
Speed isn't a stat, per se. Speed influences how many actions a Pokémon can undergo per turn. For example, a Pokémon that has used agility would normally get a x2 multiplier in the main games. In this however, it means the Pokémon (and every ally in the room) can perform another action that turn
Natures that would normally benefit/hinder a stat no longer does so in this game
If a Pokémon has more than one ability in the main series, the Pokémon will have both at the same time in this game
There's an IQ system, which I can't be bothered to explain
There is what's know as a 'body' stat. A Pokémon's body can vary between 0-4, and the entire party must not exceed an overall body of 6. A maximum of 4 Pokémon can come in an adventure at one time
There is a hunger mechanic. This isn't in Gates to Infinity, but it basically governs how well-fed the Pokémon is. Only the lead Pokémon is affected by hunger, and once it depletes, you begin losing health
This OP originally had more information in it. But, with Tonton's departure from the run, I had to remove most of it. I don't know what to add here, sorry