Can one both say : "I work from 8 to five", "I work from 8 till five" ?
I think both the sentences do not make any sense without any symbol of time expression. If you say: I work from 8 am to 5 pm. Or I work from 8 to till 5 o’clock, then the meaning is exactly the same. You can use any one of them.
Please remember to use from…to in a sentence to identify two extremes of a range; as: He spoke every thing from A to Z. It makes sense because these are the first and last letters of the alphabet, but She tried every exercise from swimming to running is not proper as these are examples of two different exercises. We can express this as: She tried all sorts of exercise incuding swimming and running Often when we are tempted to use “from . . . to” it would be better using proper expression as clarified above.