Apm2.8 drone motor decrease after full throttle

after completing the initial setup during flight test when i raise the throttle to full speed the drone motor stops spinning or decrease the speed

That test is invalid, because the copter is on the ground.

While the copter is on the ground the only test you can do is the mission planner motor test.

i have completed all the initial setup and when i try to fly it this happend how can i solve it

Explain in detail exactly what you did so far, and the results you got.

let me share the video
so u can see what iam trying to tell

I think the motor connection order is incorrect

Have the escs been calibrated?

yes sir

every step is completed

still iam getting the same problem what to do

Replace the Flight Controller with a supported one so you can get greater assistance with problems you encounter. Typically we would ask for a flight log but the data contained in flight logs from V3.2.1 is limited and not many around can troubleshoot from them.

what flight controller u suggest ?

There are many supported choices depending on your need and budget:
Ardupilot Flight Controllers

so the only option is to change the flight controller and there is not any other option regarding my problem ?

One other option is to wait for someone that uses that old controller to help you.
But there are almost no experienced users using that controller.
Experienced users know that there are better controllers and use them.
And most users no longer remember the details involved in using those old controllers from 8 years ago. Sorry.

Exactly. Even the Pixhawk has been around a long time:

Pixhawk

Nevertheless my suspicion is that the ESCs are not correctly calibrated.
And that a open-loop ground test is invalid.

let me recalibrate from first for the one last time