Can you take a photo with voice commands?

no, you can take a screen shot with assistive touch though. You may like the app camera+ you can set a timer and take a photo with a timer. The built in camera can also do this, but it takes a burst photo.

Not to my knowledge using the native Photos app. There are apps in the App Store that claim to do this but I have not found one that is highly rated. Maybe someone else can recommend one.

Try this one.

Voice Command Camera free by GOAPPS

https://appsto.re/us/TQbPG.i