Why the Download Question Dominates Search
Because this format spread through phones rather than websites. Someone is sent a link, plays a few rounds, and immediately looks for an app — the assumption being that the real version is the installed one. In practice the reverse is closer to true: the web build is the version the operator maintains directly, and the apk is the layer where copies get inserted between them and you.
The practical rule that follows is unglamorous. If you can play in a browser, do. If you install, install from a listing where a publisher name exists. And never accept a file from a chat, however many people in that chat say it works, because none of them checked the payout table either.
Old Versions, iOS and "Not Available in Your Region"
Three recurring search themes worth answering directly. Old-version downloads are almost always a mistake: an outdated client points at payment routes the operator has retired, and it cannot be updated from within. iOS builds for this category are rare, and pages promising them usually deliver a configuration profile instead of an app, which is a far larger permission than it looks. And a build that is unavailable in your region is unavailable for a reason that a sideloaded file does not fix — it just moves the problem to the withdrawal stage.
If you have not yet worked out how a round is settled, start with the mechanics on the big small game guide. For what the installed client actually contains and what each permission is for, the app and install notes go through it line by line.