Yes there is a way. You get a metal coat and trade it.
Onix evolves into Steelix, while holding a Metal Coat and traded. Steelix can also Mega Evolve, but cannot evolve into any other Pokemon.
Onix does not evolve at any lvl. You have to have it hold metal coat and then trade it. Then you will have steelix. Same goes for syther to evolve to sizzor.
ONIX DOES NOT EVOLVE BY LEVEL! To evolve Onix, equip a Metal Coat and trade it over to another game. Find trade evolutions frustrating? You can just trade any Pokemon for Jasmine's Steelix.
You cannot get Phione to evolve, it cannot evolve into any Pokémon.
Onix does not evolve at any level. If traded while holding a Metal Coat in Pokemon Gold or later, it will evolve into Steelix.You can't evolve an Onix by leve.l You have to let Onix hold Metal Coat and trade it, then it will evolve into Steelix.
Onix can only evolve through trading it with metal coat on at any level.
the same one that evolves into it in any other game! Onix! I pray you didn't mean this...
Legendary Pokemon [same with any other pokemon game for ds] cannot evolve.
Golbat will evolve if it has max friendship with its trainer which means it can evolve at any level.
In Pokemon Platinum, Porygon-2 can evolve into Porygon-Z using the Up-Grade. I do not believe it serves any other purposes.
Spinda does not evolve into any other Pokemon. Teddiursa evolves into Ursaring at level 30.
Same way you evolve a Machoke in any other Pokemon game. You have to trade it to a different generation four Pokemon game. (ex. Diamond/Pearl/Platinum or HeartGold/SoulSilver)