I've been able to date Jake/Nate on Hard mode but not gotten the "good" ending. I've not been able to date Malik at all on Hard mode, good or bad ending!
Viewing post in Help needed for Jake/Nate and Malik routes on Hard setting
Here's some hard mode Malik tips: https://itch.io/t/1639669/malik-on-hard-mode
I'm not aware of any walkthroughs at this time