"He has a blue flower."
Translation:Li havas bluan floron.
It's not the most common word order, and so it the maintainers haven't added it as an alternative yet, but it's grammatically correct. You can report it if you want.
Esperanto's flexibility means that an English sentence can often have many possible, valid Esperanto translations, and maintainers can't think of them all beforehand and add them as accepted alternatives. Instead, they rely partly on reports from learners, especially since Esperanto is still in beta.
Correct sort of. You run the risk of sounding like an Esperanto Yoda if you do that. Despite rumour, there IS an accepted word order in Esperanto. Sentence decipher to you otherwise every have. :-)