Can you recover recovery mode after erasing HDD?
If you have properly created a Mojave USB flash driver installer, inserted the flash drive in a USB port on the Mac and booted to the Startup Manger, then the an icon will appear representing the flash drive. If this does not happen, then either the flash drive was not plugged directly into the Mac or the flash drive was not properly created. In other words, most likely there is something wrong with the DMG image or something wrong with the way you transferred to the flash drive.

As for the two options:


Use bless , which is only present on macos and requires physical USB stick not DMG/iso image.


  The bless could could be used to avoid using the Startup Manager. However, a properly created Mojave USB flash drive installer would appear in the Startup Manager. Besides, you have no way to execute the bless command.

Recovery mode where you can configure drive to become bootable or at least check why it is not.


  You have erased the any recover volumes that may have existed on your Mac. The only ways left to boot to Recover mode would be from an external drive or the internet. So far you have stated you can not boot from any external sources. In the comments, you have stated that you are to afraid to use the internet.



A good reference on how to install macOS can be found as the accepted answer to the question: How can I download an older version of OS X/macOS?