I have played These games without cheats
Red Version
Venusaur Lv: 62
Gyardos Lv: 45
Mewtwo Lv: 76
Kabutops Lv: 56
Kadabra Lv: 79
Dragonair Lv: 42
Yellow Version
Picachu Lv: 88
Charizard Lv: 60
Blastoise Lv: 38
Kingler Lv: 48
Mewtwo Lv: 74
Onix Lv: 53
I Just Brought Cystal Version
Bayleef Lv: 26
Shiny Hoothoot Lv: 14
Unknown(G) Lv: 12
Unknown(D) Lv: 14