

Q2: Does <Overflow> apply when I use this card's All Turns effect to place this card in the digivolution cards of the played Guilmon?
No, it doesn't. <Overflow> applies when a card from the battle area or from under a card is placed into another area. In this case, it doesn't apply because a card from the battle area is placed under another card.
Q3: What does an "add X000 to the maximum your DP-based deletion effects can delete" effect do?
Such effects increase the maximum value shown for DP-based deletion effects. For example, while "Your Turn Add 1000 to the maximum your DP-based deletion effects can delete" is activated, "When Digivolving Delete 1 of your opponent's Digimon with 3000 DP or less" will allow you to delete an opponent's Digimon with 4000 DP or less.
Q4: If "add X000 to the maximum your DP-based deletion effects can delete" is activating, can the maximum be increased for an effect such as "delete 1 of your opponent's Digimon with DP less than or equal to this Digimon's DP" that references a Digimon's DP for deletion?
No, it can't be increased. You can't increase the maximum of a DP-based deletion effect that doesn't show a numerical value.
Lv.6 Megidramon ACE LM-026 P Mega | Virus | Evil Dragon/Four Great Dragons [Hand] [Counter] <Blast Digivolve> (Your Digimon may digivolve into this card without paying the cost.) [On Play] [When Digivolving] Delete 1 of your opponent's 11000 DP or lower Digimon. [All Turns] When this Digimon would leave the battle area, play 1 [Guilmon] from its digivolution cards or your trash without paying the cost. If this effect played, place this Digimon as the played Digimon's bottom digivolution card. (Rule) Name: Also treated as [ChaosGallantmon]. --- [All Turns] Add 5000 to this Digimon's DP deletion effects' maximums.
Lv.6 Megidramon ACE LM-026 P Mega | Virus | Evil Dragon/Four Great Dragons [Digivolve] Lv.5 w/[Growlmon] in name: Cost 3 [Hand] [Counter] <Blast Digivolve> (One of your Digimon may digivolve into this card without paying the cost.) [On Play] [When Digivolving] Delete 1 of your opponent's Digimon with 11000 DP or less. [All Turns] When this Digimon would leave the battle area, play 1 [Guilmon] from this Digimon's digivolution cards or your trash without paying the cost. If a card was played by this effect, place this card as the bottom digivolution card of the played Digimon. (Rule) Name: Also treated as [ChaosGallantmon]. --- <Overflow (-4)> (When this card would move from the battle area or under a card to another area, lose 4 memory.) [All Turns] Add 5000 to the maximum this Digimon's DP-based deletion effects can delete.
Lv.6 Megidramon ACE LM-026 P mega | Virus | Evil Dragon/Four Great Dragons [Digivolve] Lv.5 w/[Growlmon] in name: Cost 3 [Hand] [Counter] <Blast Digivolve> (One of your Digimon may digivolve into this card without paying the cost.) [On Play] [When Digivolving] Delete 1 of your opponent's 11000 DP or lower Digimon. [All Turns] When this Digimon would leave the battle area, by playing 1 [Guilmon] from this Digimon's digivolution cards or from your trash, place this Digimon as that Digimon's bottom digivolution card. (Rule) Name: Also treated as [ChaosGallantmon]. --- <Overflow (-4)> (As this card moves from the battle area or under a card to another area, lose 4 memory.) [All Turns] Add 5000 to the maximum DP you can choose with this Digimon's DP-based deletion effects.
Lv.6 メギドラモンACE LM-026 P 究極体 | ウィルス種 | 邪竜型/四大竜 [手札]【カウンター】≪ブラスト進化≫(自分のデジモンをこのカードにコストを支払わずに進化できる) 【登場時】【進化時】DP11000以下の相手のデジモン1体を消滅させる。 【お互いのターン】このデジモンがバトルエリアを離れるとき、このデジモンの進化元か自分のトラッシュから、「ギルモン」1枚をコストを支払わずに登場させる。この効果で登場したなら、このデジモンを登場したデジモンの進化元の下に置く。 〈ルール〉名称:「カオスデュークモン」としても扱う。 --- 【お互いのターン】このデジモンのDP消滅効果の上限+5000。