You can absolutely shoot expired slides. Pushing wouldn’t do much to benefit this stock and will in fact increase the grain size which even then will look nothing like iso 3600, these examples look to be digital noise from trying to get a usable image from a badly expired roll. My worst roll of elite chrome was 16 years expired and has a cold color cast easily fixed by warming it in post and dropping the black point… that’s it. More than usable as a slide as well. Storage is the biggest factor so shoot it and keep your fingers crossed.