"I give flowers to my older brother."
Some questions ago I gave the freaking flowers to Mr. Tanaka and this was acepted: 花を田中さんにあげます Now I use the same structure: 花をあににあげます And it's incorrect... How is it? Should this be correct too, the previous incorrect or is there something I am missing that makes the first acceptable and not the second?
No, you use humbling expressions, when talking about your own family, so use あに.
The pronounciation of あげ sounds wrong. It sounds like "ame", but shouldn't it be pronounced "age"? Or is this a special case?
??? I give to my older brother flowers.
✔ I give flowers to my older brother.
Duolingo's translation is good.
I believe as long as the partcles of に and を are correct, either order is fine. Times like yesterday or today typically go first, but the outside of the verb being last, the order isn't strict in Japanese.
Sentence order isn't as important in Japanese as it is in English. All that matters is that the verb (あげる) is last.