F4 visa renewal & change of address & number

As of 2015,

You can renew your F4 visa only 2 months before it ends.  So you can't renew it 6 months before your visa expires.

Also to change your address, you just have to go to your nearest "gu-chung" (city or district hall) before 14 days after moving. 

Toll free number is 1345.

You can get to a rather friendly voice with different languages.

Hope that helps anyone.