Default [Q] downgrade

Hello..

I want to ask something.I want to downgrade my s3 to android 4.1.2 and i come up to this on sammobile(attachment below).My phone gives me with *#1234# the following : AP :I9300XXUGMK6 CP : I9300XXUGMK6 CSC : I9300COAGML1
My problem is that the 4.1.2 version has different status than that and i am afraid of bricking the phone.Is this safe to dowload this rom?

Thanks in advance(noob for s3 here :P)

Edit : i saw that screenshot cannot be seen because of ads
info about screenshot is here
Model Country/Carrier Date Version PDA CSC Kies
GT-I9300 Romania (Cosmote) 2013 December 4.3 I9300XXUGMK6 I9300COAGML1
GT-I9300 Romania (Cosmote) 2013 September 4.1.2 I9300XXEMH1 I9300COAEMH1
Attached Thumbnails
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Current Phone 1 : Samsung galaxy S3 GT-I9300
Rom : Echoe_llusion_ultraslim_ml4
Android version : Echoe 4.3 jellybean tw

If I helped you click thanks