So, I've tested it on my phone and it works.
Here is what I did, I simply added my cell phone number to the Fwd No Answer under sets-active sets-line access- properties and changed the Fwd Delay to 3. The format for the number was 9xxxxxxx.
As far as the rest of the phone configuration, I didn't have to change anything, but I did look at Sets-active sets-capabilities and preferences-capabilities. Allow redirect is not checked, but redirect ring is checked.
Hope this helps.
By the way, I didn't have to do anything with feature 4. This of course means that I'd never get a voicemail, but the cell phone does have voicemail and I'd see that before I'd see my desk voicemail, which is what the user is wanting, so it works great!