I just learned than in the GSC games you can fight some Gyms in any order. Does this also apply in SoulSilver? If yes, which gyms are they?
In the Johto games, you have to fight the gyms in order until the Ecruteak gym. Then, you can either go left from Ecruteak and reach Olivine City, where you fight Jasmine's Steel type gym and then Surf to Cianwood for fighting Chuck's Fighting type gym. Orelse you can go right from Ecruteak and reach Mahagony Town, where you have to fight Pryce's Ice type gym. After beating Pryce, you have to return toGoldenrod for saving the Radio Tower from Team Rocket. So, well you can fight the Gyms after Ecruteak in any order. I suggest going to Olivine first, as that will be easier.
Source: Experience and https://bulbapedia.bulbagarden.net/wiki/Appendix:HeartGold_and_SoulSilver_walkthrough/Section_6
(Check the Second Paragraph)
Hope I helped :)
Yes, you can, but only for the Chuck, Jasmine, and Pryce.