I think ‘amdana ti’ is ‘about you’ and ‘i ti’ is ‘to you’ and perhaps ‘for you’ but some people seem to use ‘i ti’ for ‘about you.’
Is it interchangeable?
I ti is to you, but you might use it occasionally where in English you would use for you. Amdanat ti is about you, but you may also use it where in English you would use for you. It might be easier to not think of them in terms of direct English translations ;).