BIOS
This is described in
docs\config.txt. MAME-RR needs a BIOS name command-line argument to set the BIOS file.
mame-rr mslug -bios japan
This command will launch
Metal Slug - Super Vehicle-001 with
Japan MVS (Ver. 3) BIOS.
Here's the list of BIOS names in neogeo.zip (note that "euro" is marked as default, so it's used automatically if you don't specify the BIOS name):
name="euro" description="Europe MVS (Ver. 2)" default="yes"
name="euro-s1" description="Europe MVS (Ver. 1)"
name="us" description="US MVS (Ver. 2?)"
name="us-e" description="US MVS (Ver. 1)"
name="asia" description="Asia MVS (Ver. 3)"
name="japan" description="Japan MVS (Ver. 3)"
name="japan-s2" description="Japan MVS (Ver. 2)"
name="japan-s1" description="Japan MVS (Ver. 1)"
name="mv1c" description="NEO-MVH MV1C"
name="japan-j3" description="Japan MVS (J3)"
name="japan-hotel" description="Custom Japanese Hotel"
name="uni-bios_2_3" description="Universe Bios (Hack, Ver. 2.3)"
name="uni-bios_2_3o" description="Universe Bios (Hack, Ver. 2.3, older?)"
name="uni-bios_2_2" description="Universe Bios (Hack, Ver. 2.2)"
name="uni-bios_2_1" description="Universe Bios (Hack, Ver. 2.1)"
name="uni-bios_2_0" description="Universe Bios (Hack, Ver. 2.0)"
name="uni-bios_1_3" description="Universe Bios (Hack, Ver. 1.3)"
name="uni-bios_1_2" description="Universe Bios (Hack, Ver. 1.2)"
name="uni-bios_1_2o" description="Universe Bios (Hack, Ver. 1.2, older)"
name="uni-bios_1_1" description="Universe Bios (Hack, Ver. 1.1)"
name="uni-bios_1_0" description="Universe Bios (Hack, Ver. 1.0)"
Double resolution
This is described in
docs\windows.txt.
mame-rr mslug -resolution 640x480 -max -prescale 2