Portrait mode does not have the option to adjust the focus/blur after taking the photo. Only by selecting the blur effect before taking the photo
Portrait mode works for me on all objects for live focus. However, on the right hand side there is a yellow circle, click on that as you might have 'Big Circle Face' selected instead of 'Blur'
After taking the photo, click on it in your camera roll and at the bottom of the image it'll say 'Change background effect' click that and you can use the slider to change the amount of blur.