Preparing for Time Stranger without having ever played any Digimon game

Im viewing videos about devolution, personality and so on cause I would start the game on hard difficulty. Everything seems confusing, like trying to obtain specific personality for an evolution or a stat boost, same for training, that gives blue stats (a boost): in this case I understood that if you de-evolve and then digivolve again after getting friendship via food you raise the blue stat, true?

What else should I know or avoid to do to play on hard?