firstly.....ive gone to every location for the 1/35 soldiers and wasnt able to get all 12 despite going out of my way to make sure. so im not able to obtain the omni plus materia.
u'll need to use blackchocobo or simular to edit ur save file. the one in shinra raid hq staircase gives an alternative item.
secondly i noticed a number of enemies in the documentation do not appear in game at all seemingly. unsure how to make them appear.
type a/b differences alongside hard/normal mode difference.
does hard mode only give enemies more hp and maybe more dmg? cuz toggling it on didnt seem to change much in terms of the battles.
higher level more hp 1/4 exp no battle gil. There is a few enemies where bug exists which gives gil. theres also after midgar area when escape hard mode will toggle off. (motorcycle section)
so u'd require to use a savepoint to toggle it back on.
What enemies were u looking for an example perhaps cacturs at desert prison is one i can think of which spawns more rarely at the same area as the landworms spawn at.