

Q1: If the 3 cards revealed for this card's effect include only either 1 card with the Light Fang trait or 1 card with the Night Claw/Galaxy trait, can I just add that 1 card to my hand?
Yes, even if you only reveal one of the applicable cards, you can still add it to your hand.
Q2: If the 3 cards revealed for this card's effect include 1 card with the Light Fang trait and 1 card with the Night Claw/Galaxy trait, can I choose to only add one of them to my hand, and place the remaining cards at the bottom of my deck?
No. If you have cards that are targets of this effect, you must add as many cards to your hand as possible.
Lv.4 Lekismon EX5-017 R Champion | Data | Beastkin/Night Claw [On Play] [When Digivolving] Reveal the top 3 cards of your deck. Add 1 card with the [Night Claw] trait and 1 card with the [Light Fang] or [Galaxy] trait among them to the hand. Return the rest to the bottom of the deck. --- [Opponent's Turn] This Digimon gets +2000 DP.
Lv.4 Lekismon EX5-017 R Champion | Data | Beastkin/Night Claw [Digivolve] Lv.3 w/[Night Claw]/[Light Fang] trait: Cost 2 [On Play] [When Digivolving] Reveal the top 3 cards of your deck. Add 1 card with the [Night Claw] trait and 1 card with the [Light Fang] or [Galaxy] trait among them to the hand. Return the rest to the bottom of the deck. --- [Opponent's Turn] This Digimon gets +2000 DP.
Lv.4 Lekismon EX5-017 R champion | Data | Beastkin/Night Claw [Digivolve] Lv.3 w/[Night Claw]/[Light Fang] trait: Cost 2 [On Play] [When Digivolving] Reveal the top 3 cards of your deck. Add 1 card with the [Night Claw] trait and 1 card with the [Light Fang] or [Galaxy] trait among them to the hand. Return the rest to the bottom of the deck. --- [Opponent's Turn] This Digimon gets +2000 DP.
Lv.4 レキスモン EX5-017 R 成熟期 | データ種 | 獣人型/ナイトクロウ 【登場時】【進化時】自分のデッキの上から3枚オープンする。その中の特徴に「ナイトクロウ」を持つカードと特徴に「ライトファング」/「銀河型」を持つカード1枚ずつを手札に加える。残りはデッキの下に戻す。 --- 【相手のターン】このデジモンをDP+2000。