Hello, there is something on you tube that shows you that you can catch a mewtwo with a
pokeball before obtaining the first gym badge. Not only is there that cheat, but i think
there is, on you tube, a 'working' cheat shows you that you can catch mew in lavender
town. Trust me, these cheats work and they can all be found on these links:
The best pokemon glitchs!
New!!! Pokemon yellow – mewtwo glitch
On you tube there are other working good famous/infamous cheats such as: the infamous
truck glitch, all three starters, 'lets glitch pokemon', jkl8nfay, mewtwo before e4? And
finely pokemon yellow legendaries. Hope i helped,
Flaffy11

P. S: if you can do cheats, you can do ace glitches..
P. S. S you have spelt the title of the game wrong. The 1999 games is 'pokemon yellow:
pikachu special edition'.