In Pokemon Soul Silver can you explore the Kanto region?

yes. you're from johto, when you beat the elite 4 and become champion, you will be transport to your home and then talk to prof. elm. he give you a ss ticket ship. so after that you go to olivine city and then there's a harbor below. go there and take the ship. when you're in the ship, find the lacky worker and the go below the ship and pass through the guy. then go to the captain room to get the old man kid. and then you completed it go to your room and sleep. when you woke up, go to the ship entrance and go out and you're arrived in kanto.hope this help!