Too Many Bones: Undertow

No — Atk and Def dice in your Backup Plan do NOT count against your Atk/Def Stat, and you may use your Backup Plan once per turn by removing the BP (crossed-tools) die to activate that BP skill (see p.36 and p.22).

No — you declare a single target for the turn before choosing/rolling dice, and any effect that uses the word “target” must be used on that same target (exceptions apply only to effects that don't use the word “target”) (see p.36).

When KO’d your Gearloc chip and Ini die are removed to your Prep Area, all Active, Locked, and Backup Plan dice are removed (Skills are Exhausted); Loot stays with you but is not usable while KO’d (see p.23).

Melee Baddies will never target a unit they have no route to; they target the closest opposing unit with the fewest-steps route (ties use the target/compass rule, then party choice), and moving diagonally between two adjacent Baddies is allowed because that isn’t considered passing through a unit (see p.22 and p.37).

No — applying Skill dice that deal damage is not considered an “attack”; only rolling Atk Dice on a target is an attack, and Gearlocs must have a valid target in attack range to roll their Atk Dice (see p.12 and p.37).