Boot system into different targets manually
You need to modify the boot command. On the grub2 screen where it shows the boot options, press e to edit.
On the line that starts with linux16, append one of these possible values:
systemd.unit=emergency.target systemd.unit=rescue.target systemd.unit=multi-user.target systemd.unit=graphical.target
With one of those items added to the kernel instruction, press CTRL+X to boot the kernel.