One of the mechanics from the mainline Pokemon games that Pokemon: Infinite Fusion does not have is trading. As many trainers know there are a variety of Pokemon that evolve only through trading. Pokemon such as Kadabra, Graveler and Haunter all evolve through trading in the main series.
To evolve these Pokemon in Pokemon: Infinite Fusion, you will just need to level them up. Once these Pokemon hit level 40 they will evolve on their own with no need to trade. Some fan-made games such as Pokemon Unbound solved this issue by creating an item called a trade stone which allows these Pokemon to evolve through an item. Pokemon Infinite Fusion is done through level-ups however.
There are other Pokemon evolutions that have changed as well. Since this game doesn’t have a recorded friendship level, these Pokemon will just evolve by levelling up or using their respective stones. For example you no longer need friendship during the day to evolve an Eevee into an Espeon. Just simply use a Sun Stone.
You can see a great resource on evolution changes in Pokemon: Infinite Fusion here.