These runs have a few rules to them, those rules being:
1) Only the main pokemon may take part in battle
2) Other pokemon may be caught for HM and other overworld moves (e.g. dig)
3) No items are to be used in battle
4) All gym trainers must be defeated before their respective gym leader
5) No evasion moves (double team, minimize)
6) No saving between Elite 4 Members
7) Not exactly a rule, but why 148 and not all 152 (including Missingno)? Because Caterpie, Metapod, Kakuna and Magikarp have no way to damage ghost type pokemon in gen 1 due to Struggle being a Normal type move instead of typeless.
discord: / discord
patreon: / pondoor