Your device must be on bootloader version:
I9300IDDUBQE2
You will find I9300IDDUBQE2 there :
https://samfw.com/firmware/GT-I9300I/bit/all/av/KitKat(Android%204.4.4) (choose your country/CSC)
or there :
https://samfrew.com/fr/download/GALAXY__S__Ⅲ__Neo__/58z2/INS/I9300IDDUBQE2/I9300IODDBPF1/ (choose your country/CSC)
.
OTG only works on my Galaxy s4 and s4active but not on my s4mini.
Charging during OTG don’t works
MHL/hdmi or MHL/vga don’t works
For my devices
scrcpy works