Yes hotdogs will float when they are done boiling or deep frying.
Hotdogs really are already fully cooked when you buy them so hotdogs are always done and ready to eat and actually you can eat the hotdogs directly from the package.
My younger brother used to eat hotdogs out of the package when he was 3 years old and I thought he was eating raw hotdogs but actually the hotdogs are cooked so it was safe for him to eat those hotdogs.
When boiling hotdogs it takes around 5 minutes and when the boiled hotdogs have become plump they are ready to serve or eat.