Mareep can't learn Thunderbolt in Heartgold version from levelling up. Flaafy and Ampharos can't learn it that way either.
It can learn Thunderbolt through TM.
Yes, it learns Thunderbolt at level 26.
It will learn "Thunder" (with an attack of 120 and accuracy rate of 70), a far better move than "Thunderbolt", at level 61. But it does not learn "Thunderbolt". You can, though, give it a "Thunderbolt" TM =)
By TM, Lugia can learn Thunderbolt, Thunder, Shock Wave, Charge Beam, and Thunder Wave.
Pikachu learns Thunderbolt at lvl 26 in Pokemon Yellow.
Pokemon cannot learn Yawn in Pokemon Silver.
Bellsprout, abra, mareep those are all I know
The Tm's are moves that can be tought to certain pokemon e.g:pikachu can learn thunderbolt.
There is no Thunderbolt TM or tutor in Gold or Silver but in Crystal a man near Goldenrod's Game Corner will teach one Pokemon Thunderbolt, Ice Beam, or Flamethrower for 4000 coins on Wednesday and Saturday after you beat the Elite 4. You get one shot a day. Other than that the only way to learn it is to breed for it or level up for it.
thunder thunderbolt iron tale spark
No it cannot not even using a TM