Legality depends on the tournament format -- Greenseeker can be legal in some formats and banned or restricted in others
The edges and corners have many white spots, the surface usually has scratches, and the card usually has accumulated some dirt on its surface

Heres a short list of all the important cards featured in each set: HGSS: Cleffa, Tyrogue, Jumpluff, Ninetales, Pichu, Pokmon Collector, Pokmon Communication, Professor Oaks New Theory, Copycat, Rainbow Energy, Double Colorless Energy, Donphan Prime, Typhlosion Prime, Blissey Prime UL: Rare Candy, Jirachi, Suicune/Entei Legend, Shaymin, Kingdra Prime, Tyranitar Prime, Lanturn Prime, Judge UD: Sages Training, Vileplume, Weavile, Rayquaza/Deoxys Legend, Muk, Sages Training TM: Junk Arm, Seeker, Twins, Rescue Energy, Almost Every Single Prime (Magnezone, Mew, Yanmega, Gengar, etc.) CoL: Jirachi, Pachirisu, Cleffa, Tyrogue, Ninetales, Sages Training, Professor Oaks New Theory BW: Emboar, Reshiram, Zekrom, Cinccino, Reuniclus, Zoroark, Pokmon Communication, Professor Juniper EP: Pokmon Catcher, Tornadus, Gothitelle, Cheren This is just an introductory list, but Im sure just by looking at it its easy to see how tough it can be to build a deck

In a meta where you need a versatile and reliable removal spell this is the thing to play
The Demo Deck is from 1998, not 1999
The Space-Time Smackdown set will be released on the app on January 30, primarily featuring Pokmon from the Nintendo DS games Diamond and Pearl