Can one both say : "I work from 8 to five", "I work from 8 till five" ? And does it have the same meaning ?
Yes, they have the same meaning. It's more common to say, "I work from 8 to 5," or to say, "I work 'till/'til (short for "until") 5:00. (Said without the start time.) Although it's less common to say, "I work from 8 'till 5," the meaning is exactly the same.