<nephew> (now often ['nefju:] rather than ['nevju:])
Not often: ALWAYS, at least in AmE.
In certain non-stressed positions, [v] often seem to have reduced
voicing, almost merging with [f], at least to my ear.
There's also a class of BrE/Oz native-speaker that turns thorn
(unvoiced th, as in 'thorn') into [f] (bathroom --> baffroom, death