When downloading a folder with a question mark

Greetings to all!

When I downloaded my iMac, a folder with a question mark appeared instead of an apple.

The following measures were taken:

1. Launch macOS from an external drive ("GPT (GUID Partition Table)"), but this time a prohibitory sign appeared during boot.

2. All external devices are turned off to avoid conflict with the periphery.

3. Log in the safe mode failed, ⇧Shift and ⇧Shift + ⌘Cmd + V do not work.

4. Resetting NVRAM or PRAM also did not help.

5. It is not possible to enter restore mode, ⌘Cmd + R command does not work.

Help determine the cause of the malfunction of my iMac, I'm inclined to believe that the HDD is out of order, or the loop from the HDD to the motherboard is faulty.