Final update - I filled the Pokédex in Crystal Version as much as possible without trading or glitches. My legendaries easily defeated Red's high-level team. (Links to previous posts in comments) :
How to transfer old Pokémon from Bank to Pokémon Home - Polygon
My 16-year-old Pokémon from Crystal will join me in Ultra Sun | PokéCommunity Daily
Pokémon Crystal Version for Nintendo 3DS - Nintendo
Pokemon Crystal Coming to 3DS on January 26th – GameSpace.com
Pokémon Crystal, Trading Card Game, Silver and Gold reappear atop the Japanese Nintendo 3DS eShop charts for the week ending September 19 | Pokémon Blog
How to self-trade with your 3ds. : r/pokemon
How to transfer to Pokemon Home from DS, 3DS, Switch, and Pokemon Go - GameRevolution
Pokémon Trading Card Game Review (3DS eShop / GBC) | Nintendo Life
Pokémon Gold, Silver, and Crystal VC: International Trading / Cross-language Compatability - YouTube
How to transfer Pokemon from older games to newer ones
Trading - Pokemon Gold, Silver and Crystal Wiki Guide - IGN
Buy Nintendo 3DS Nintendo 2DS Crystal Blue System Trade-In | eStarland.com
My Nintendo adds Pokemon discounts, Pokemon Crystal wallpaper in North America
Pokémon Crystal, Trading Card Game, Silver and Gold reappear atop the Japanese Nintendo 3DS eShop charts for the week ending September 12 | Pokémon Blog
Trading - Pokemon Gold, Silver and Crystal Wiki Guide - IGN
Pokémon Crystal coming to 3DS in a cardboard box | Eurogamer.net
Pokémon Crystal Version for Nintendo 3DS - Nintendo
Pokémon Crystal - Virtual Console Updates
Pokémon Crystal arrives on Nintendo 3DS for $9.99 - The Tech Game
A Look Back at Mobile System GB, Pokémon Crystal's Online Service | PokéCommunity Daily
Updated] What happened to Pokémon Crystal's eShop release? | PokéCommunity Daily
nintendo 3ds 3dsxl 2ds pokemon second generation - Is it possible to trade Pokémon from Silver virtual console to Fire Red or Diamond? - Arqade
Pokémon Crystal coming to 3DS in a cardboard box | Eurogamer.net
Pokemon Crystal announced for the 3DS Virtual Console, out on January 26
Pokémon Home flowchart makes the complex transfer process easy