If I grew up in the suburbs of Detroit but moved to Detroit in my early 20s can I say I'm from Detroit?

saying your from Detroit means you're from the area. If you go to any other State and say "I'm from from Livonia" they have no clue what you're talking about. Plus Livonia is close enough to Detroit

Sure, since that is now your permanent residence, consider yourself a Detroiter. I live in Texas and I usually tell people I am from the large metro in which I live, especially for people outside my immediate area. You will find that many people outside Michigan, or perhaps a nearby state don't know where Livonia is. Nothing wrong with Livonia, it's just most people have heard of Detroit, not so much Livonia. For example, I could say I live in West Lake Hills, Texas. Most people outside Texas don't even know where that is, so it would be easier to say I am from the Austin area.

Will anyone care if you do?

It kind of depends who's asking, and how much detail they need to know.

If  you're visiting the UK and people realise you're from the US and ask where'in the US, it's fine to say 'Detroit'.If you're inside the US generally you can say you're from Detroit.

But if you're IN Detroit and people ask, obviously you say 'I gew up in Livonia but I've lived in the city most of my adult life'.

I've noticed over the years that many Americans don't understand the difference between an in-depth interrogation and a simple off-hand conversational question. People get all tied up about how their work colleagues ask them really intrusive  questions like 'Are you married?' or 'Do you have any children?'People, these are not difficult. Nobody's asking to hear your life story; they just want something to hang a basic conversation on.

Same with 'So, where are you from?' Just give the answer that will satisfy their very superficial curiosity and let them chat.

It’s totally up to you to say where you are from

For me in the UK, anywhere near Detroit which "looks to" Detroit as its centre of activities is Detroit as a general expression of district.

If I were to meet you if you were visiting the UK and you told me that you came from Livonia, Michigan, I would ask you for the name of a well-know city near there, and you would naturally reply "Detroit". Then I would understand where you came from. For an oldie like me the association wold be "Motown".

Who is likely to question you? Unless there is a distinct difference in accent, nobody will say a word.

Something tells me you aren't from Detroit. You posted an almost identical question about being from Oakland.

Yes, you can say that. When people ask where you're from, they aren't necessarily asking your entire life history.

From? Not really.

Live in? Yes.