Sorry not really good in english.
For me I usually check the store page and add the game to cart, when checkout you will usually see red text like this in new releases or upcoming games. Like csgo, not only region locked but cross region trading locked.
There are some ways to check game, like adding steam extension and checking steamdb.
For scam, there will be tons of scam because of this changes, we usually trade using the trade window, now you can't use trade window since the game is not tradable(only giftable). In steam trading, people usually pay tf2 keys, dota 2 treasure keys, csgo keys as they are consider steam currency.
And yes your correct, this is probably valves protection against fraud, so many carded games last few months.