you get fire and ghost pokemon on cinnabar island and u cannot get your pickachus move
back. u move snorlax with the poke flute.u catch new pokemon in safari zone thats all i
know i just beat the game right now

what poke version u use if u use pokemon red,blue,yellow vesion (.gbc)
you can follow the answer above. if u use pokemon fire red or leaf green (.gba)
thundershock: go to move deleter delete your flash
u can use thunder,thunderbolt, thundepunch that iknow better dan thunder shock. or maybe
thunde shock available as a tm move if u want it back.
--> important <--
cinnabar island is the 7th gym and u just collect the vermillion gym its too far away get there. so be patient.
there is away to complete 30 pkmn
evolve nidoran F to nidrina and kkeep lvling till become nidoqueen. and nidoran M-> nidorino->nidoking
rattata->raticate every pokemon evolve is counted in poke dex
zubat-> golbat
drowzee-> hypno
ekans-> arbok
geodude->graveler->golem(trade)
pidgey->pidgeot->pidgeotto
spearow-> fearrow
that i know to complete poke dex without any much explain

u can use moonstoon to evolve
nidoranf->nidorina
nidorina->nidoqueen
nidoranm->nidorino
nidorino->nidoking

there is a limited moonstone available in game so use wisely