wrote:

When using FS2004 for practice IFR approaches, can I start my flight
from said 4,000 over an IAF? If yes, how do I do that.

Another way no one mentioned is to use the map.

Open the map, and just click and drag the airplane icon to whatever
location you want it. There are boxes, as I recall (haven't done it for
a long time) to set aircraft altitude, heading, and airspeed.