May I ask how do you request songs? 
Sorry to say this, but the request applications had already expired since January 25th. But I can show you how it works using a sample for MA3.
▼応募曲をうたってほしいキャラクター名 (Character name that you want them to sing an applicant song)
Insert idol here in Japanese
▼カバー希望楽曲名(1曲) - Song Name (must be in Japanese unless written differently)
▼上記楽曲のオリジナル歌手名 (Artist's name in Japanese)
▼曲の選考理由 (Reason you choose above song)
▼春をテーマにしたカバー希望楽曲名(1曲) (Song Name; for this one, this one must be related or have a Spring feel to it)
▼上記楽曲のオリジナル歌手名 (Artist's name)
▼曲の選考理由 (Reason you choose above song)
The rest are questionnaires
▼あなたが選んだアイドル(キャラクター)に対してのメッセージ、お願い、質問などご自由にお書きください。(※アイドルにチャレンジしてもらいたいことなど)
Message for your chosen idol.
▼今後の「アイドルマスター」シリーズへの要望があればご記入ください。
Please fill in here if there is a desire for the future of "THE IDOLM@STER" series.
▼プロデューサーネーム(掲載する場合のお名前)
Your Producer name (will be shown on the CD jacket if picked)
▼性別 (Gender)
男性 (Male)
女性 (Female)
▼年代 (Age)
Pretty straight forward.
▼都道府県 (Prefectures)
Select "その他" (Other) if you currently live outside of Japan. Otherwise, good luck.
