You know, what goes on the reverse of the card is up to you. If you are defining something written in hiragana having the kanji in the definition is helpful. If you are defining kanji, then having hiragana in the definition would still be helpful if you turned the furigana off for that particular review activity. Likely it is more helpful because the furigana could be wrong.
Yes, but the lingq definition was picked by you from a list of user-submitted definitions. You can and should edit the definitions as you pick them to match how you want to study.