I might be wrong in the first 2 gens, but I'm certain of the other ones
Kanto (Orange Islands)
- Thunder Shock
- Thunderbolt
- Agility
- Quick Attack
- Thunder
Yup, 5 moves... anime logic
Johto
- Thunderbolt
- Quick Attack
- Thunder
- Agility
This is the one I'm the least certain of, I barely watched that series and Pika's movepool was very inconsistent (He used Tackle and Leer?!)
Hoenn (Advance)
-Thunderbolt
- Quick Attack
- Iron Tail
- Volt Tackle
In the beggining of Advance, Pika learns Iron Tail in preparation for Roxanne. Then, during the Battle Frontier arc it learns its species signature move: Volt Tackle
Sinnoh (DP)
-Thunderbolt
- Quick Attack
- Iron Tail
- Volt Tackle
Its the same moveset
Unova (Best Wishes)
- Thunderbolt
- Quick Attack
- Iron Tail
- Electro Ball
Ash was just battling a Ducklett squad and suddendly Volt Tackle is replaced with Electro Ball (rip)
Kalos (XY)
- Thunderbolt
- Quick Attack
- Iron Tail
- Electro Ball
Again, nothing changes
Alola (SM)
- Thunderbolt
- Quick Attack
- Iron Tail
- Electro Web
When battling its rival, Jessie's Mimikyu, in the Thrifty Megamart trial, Pikachu learns probably its most versatile move: Electro Web.
Journeys
- Thunderbolt
- Quick Attack
- Iron Tail
- Electro Web
The champion's set stays the same throughout Journeys.
I have no idea if will learn a new move in the epilogue (Aim to be a Pokémon Master), but for now these are all of the sets
Source