Greek keyboard on iPhone

I was trying out a vocab flashcard app on my iPhone so I added a Greek keyboard to the phone. It will allow me to use regular accents but I can’t figure out how to get breathing marks, combo marks, or iota subscripts—just the simple accents. Any tips, or is the keyboard just limited that way?

I use the Hoplite Polytonic Greek Keyboard, which allows for easy combination of accents, breathings etc (and macrons if you want them). I use the Android version but it’s available on iOS too.

https://philolog.us/hoplitekeyboard.html

A second vote for the Hoplite keyboard (although its shift-lock is a bit annoying).

That works! Thanks so much.