1.
sounds like a great plan! Since you are moving these into a puzzle-making software, you likely need them in a plain list format without the categories or extra text so you can easily copy and paste them all at once.
3.
Sequoia, Canopy, Timber, Redwood, Willow, Juniper, Sapling, Foliage, Deciduous, Conifer, Oak, Maple, Pine, Birch, Grove, Woodland, Bark, Acorn, Root, River, Lagoon, Cascade, Stream, Estuary, Brook, Ocean, Glacier, Current, Waterfall, Delta, Bayou, Rapids,