iOS App with two states and mostly different content categories

I’m working on a medical iOS app for university. Our users are usually 55+ years. I’m currently struggling with the navigation flow of the app. We basically have two states, pre and post-surgery. Both states share some content but mostly have different content. I thought about using “tab bar” with changing tab bar items. So the first two tab bar items are constant, but item 3 to 5 are changing depending on the state. (The state usually only changes once) How bad is it to change the tab bar items in terms of user experience, especially for old not to experienced users? I also thought about onboarding after the state changed, to teach the ui changes.

In general:

How do you usually handle navigation for apps with two states and mostly different content:

State 1:

• Content Category A
• Content Category B
• Content Category C
• Content Category D
• Content Category E

State 2:

• Content Category A
• Content Category B
• Content Category F
• Content Category G
• Content Category H

States share category A and B, but differ with C,D,E,F,G,H

Thanks in advance :)

I can't share something real, but here an example. The state changes once after a specific event and two menu icons change as long with some content on the home / control / overview screen