I’m planning a playthrough in Heartgold with a Scizor on my team, as a Scyther either traded to my Platinum and traded back or from Platinum to Heartgold. I saw on the Move Tutor page that the only way to get Bug Bite on Scizor is by a Move Tutor in the Battle Frontier. Is there any way I can get Bug Bite on him pre-league?
In HeartGold, the only way to get Bug Bite on Scizor is to teach it at the Battle Frontier Move Tutor.
It is impossible to get a Scyther/Scizor with Bug Bite in Platinum.
Source: The Scyther and Scizor move learned page on this site
In HeartGold, the only way to teach bug bite to scizor is going to a move tutor, which is in Battle Frontier.
In Platinum, there is no way to teach bug bite to scizor, so you can't teach bug bite in platinum.
Hope it helped:)