I own one of these, easily the worst radio I have. Fine for receive but please don't hit that transmit button.
Definitely don't try 27 MHZ, or perhaps outside of the above bands at all.
Are these Yaesu, Motorola, or Icom quality? No, but they're $25.
Unfortunately people don’t realize that even if you install a firmware that allows down to 11m, even connected to a $1200 base antenna the power output will be in the milliwatt range while throwing off on harmonics.
There’s also the case of hardware inconsistency and fakes. When I hook up 4 of the included antennas to my VNA there’s pretty big variance, and I recently tested a fake Nagoya that was clearly tuned for air band and not 70cm/2m as advertised.
I pretty much only use it for experimentation and receive.
The old Baofengs had that problem, not Quansheng which are actually clean and the harmonics are within FCC specs.
However, if you hack the firmware and transmit outside the bands the radio's RF is designed to transmit on, then you will probably see all sorts of spectral weirdness.