Just had a look at the above Xperia M (C1905) ROM build.prop and it indicates the follow:
Singapore: Customised SG
######################## Customized property values #########################
ro.semc.version.cust=1274-5468
ro.semc.version.cust_revision=R1C
ro.somc.customerid=442
##### Values from product package metadata #####
ro.semc.product.model=C1905
ro.semc.ms_type_id=PM-0490-BV
ro.semc.version.fs=WORLD-i
ro.semc.product.name=Xperia M
ro.semc.product.device=C19
ro.product.model=C1905
#########################################################################
There are many 'world' releases from different countries.
I'd be interested to see if the Serbian 'world' 15.4.A.1.9 release has SMS(txt'n) character optimisation option as the 15.4.A.0.23 version did.
I know the Malaysian 15.4.A.1.9 release doesn't have an SMS character optimisation option (FYI)
Update -
Oh, and you may want to check the Wireless 5GHz regulations for the country you're in if you plan to use 5GHz WiFi.
Singapore has a different set of regulatory channels/frequencies compare to say Europe.
Checked WiFi conf on other ROMs and don't see any differences in WiFi ini between the ROM's so no reason to think Singapore would be any different as a '
world' unbranded ROM.
I did get caught out using an Indonesian Xperia M (C1905) Android 4.1 ROM once and at the time it didn't even support 5GHz WiFi (regulations for Indonesian 5GHz WiFi changed to now allow it, but not sure if that's now reflected in ROMs)
Remember the devil is in the detail.