Q1: Can I use this card's On Play effect to play a EX4-062 Kiriha Aonuma & Nene Amano from my hand without paying the cost?
Yes, you can.
Q2: Does this card's On Play effect activate when I have EX4-062 Kiriha Aonuma & Nene Amano in play?
No. EX4-062 Kiriha Aonuma & Nene Amano is a card that's also treated as Nene Amano, therefore the "If you don't have Nene Amano in play" condition isn't met and the effect doesn't activate.
Lv.4 SkullKnightmon EX4-040 C Champion | Virus | Undead/Twilight [On Play] If you don't have [Nene Amano] in play, you may play 1 [Nene Amano] from your hand without paying the cost. [On Deletion] Reveal the top card of your deck. If that card has the [Blue Flare] or [Twilight] trait, add it to your hand. Trash the rest. --- Inherited: <Reboot> (Unsuspend this Digimon during your opponent's unsuspend phase.)
Lv.4 SkullKnightmon EX4-040 C Champion | Virus | Undead/Twilight [On Play] If you don't have [Nene Amano] in play, you may play 1 [Nene Amano] from your hand without paying the cost. [On Deletion] Reveal the top card of your deck. If that card has the [Blue Flare] or [Twilight] trait, add it to your hand. Trash the rest. --- Inherited: <Reboot> (Unsuspend this Digimon during your opponent's unsuspend phase.)
Lv.4 SkullKnightmon EX4-040 C Champion | Virus | Undead/Twilight [On Play] If you don't have [Nene Amano] in play, you may play 1 [Nene Amano] from your hand without paying the cost. [On Deletion] Reveal the top card of your deck. If that card has the [Blue Flare] trait or [Twilight] trait, add it to your hand. Trash the rest. --- Inherited: <Reboot>.
Lv.4 スカルナイトモン EX4-040 C 成熟期 | ウィルス種 | アンデッド型/トワイライト 【登場時】自分の「天野ネネ」がいないとき、手札から「天野ネネ」1枚をコストを支払わずに登場できる。 【消滅時】自分のデッキの上から1枚オープンする。そのカードが特徴に「ブルーフレア」か「トワイライト」を持つカードなら、手札に加える。残りは破棄する。 --- Inherited: ≪再起動≫(相手のアクティブフェイズに、このデジモンをアクティブにする)