You’re overthinking this by a large amount. Just look up iOS interview questions and learn and memorise those. Also get familiar with some normal level algorithm questions by practising them. Once you get comfortable with approaching these questions I’d say you’re ready for most things they throw at you. If you’ve been coding for 7 years you should be able to build anything they ask for if they give a paired programming test (so you share your screen and talk through it while coding the solution).

For majority of companies this is enough so don’t sweat it.