Okeh my Question gonna be bit longer so have Patience pls :)
Lets Say we have fully loaded 747-400 at runway so l think Flaps 20 will be optimum setting for take off , let us assume as well that ATC has vector us to climb and maintain 7000 feet and then maintain 12,000 feet and so on until we maintain 33,000 feet till we start descending and finally land. Okeh my Q is
1) Right from 20 degree flaps from take off to level flight i.e. 0 degree flaps, atwhat AGL andKIASshould pilot instruct co-pilot to retract flaps until it reaches 0 ?
2) Howdoes pilot decide its good time tostart descending and should start engaging flaps until established on localizer and moreover what is AGL, KIAS and distance from airportfor each flap setting ?
Pls no dumbto my Q

The 747-400 will place bugs on the PFD to indicate the flap schedule for climb & descent. You can use those as a guideline for when to retract the flaps. Since flaps have multiple effects on the aircraft, u might or might not exactly respect the bugs.

Flaps provide greater lift but also increase drag. Use them when u need to fly slowly. You can also use them to slow the aircraft, to a limited extent, although that is not their main purpose. They must be retracted in cruise flight in order to fly at high speed.

Typically, flap retraction starts shortly after take-off so that u can accelerate to ur optimum climb speed, & u will be clean in short order. On descent, the flap schedule may be more prolonged, with a bit of flap as u slow on arrival & descend & approach the airport. You can use the pitch angle & flight path vector on the PFD to help u decide when to add flaps if u do not want to use the bugs. Take care to observe the speed limits on the placard for flaps.

Keep in mind that flaps allow u to fly low & slow, but they also create a lot of drag (especially in the more extended positions) that will require more thrust & chew into ur fuel a lot faster. You might burn twice as much with flaps mostly extended as u were burning when u started ur descent, even though you're moving a lot more slowly. If fuel is tight, this can lead to bad things if u extend flaps earlier than u have to. It can be a good reason to fly faster & cleaner until you're closer to ur destination.