Not everyone collects by set. Plenty of people simply want each Pokémon once. The Pokédex in TCGHeart flips the question: not which cards do I have, but which Pokémon do I have.
You see every Pokémon on a grid, grouped by generation. What you own is in colour, what you are missing is grey. At the top you see how much of the dex you have completed.
Forms such as Alolan, Galarian, Hisuian and Mega can be counted separately or folded under the base Pokémon, whichever you consider one slot.
Tap a Pokémon and you see every card that exists for that species, across all sets and languages. Filter by set, rarity, variant and language, and sort by price to find the cheapest way to fill that slot.
If you only collect Japanese, you set that once and the whole dex counts Japanese cards only.
Everywhere in the app you can sort by Pokédex number instead of card number or price. Your collection, the market and a set page then line up in the same order as the dex itself.
A collection holding at least one card of every Pokémon. Instead of completing sets you fill the Pokédex, from Bulbasaur to the newest generation.
That is up to you. You can fold forms under the base Pokémon or count them separately.
Yes. Pick a language and only cards from sets in that language count towards your progress.