In Australia, what is used in the classic hotdog are/were "frankfurts" or "saveloys" .(The latter is slightly different, & the name seems to have fallen out of use)
They are "pre-cooked", to the extent that they are safe to eat "straight out of the shop".
In use, they are usually boiled, & slapped into a roll with toppings to the customer's choice.
When I was a kid, at Agricultural Shows (local & State Fairs in US speak), they were boiled "en masse" in what we used to call "coppers" (the large copper tub in which clothes were boiled back in the day).
These were becoming obsolete, but conveniently many had been set up with a heating fire in portable form, & were quickly repurposed by the hot dog vendors.
You could smell the cooking "dogs" all across the Showground.
I don't know what effect all that copper residue had on my generation, but we still seem to be around in droves!

Normal sausages are always sold raw --- Vienna sausages are cooked, or somehow made safe for immediate eating.
Tinned sausages are available, but like tinned anything, are a reasonable snack, but that's it
In recent years, traditional "hot dogs" have come under strong challenge from the "sausage sizzle", where normal sausages are cooked on a grill or hot plate, & stuffed into a roll in the usual fashion.