Can I upgrade from OS 4.1.2 to the next Android OS

[Cozy Void]

I am on a Galaxy S3

 

[Rukbat]

Has your carrier released an update to the next version? (It's up to them.) According to the specs, it should update to at least 4.3.

 

[LuisPPK]

Has your carrier released an update to the next version? (It's up to them.) According to the specs, it should update to at least 4.3.

I have 4.1.2 too in my lg e450g. No updates from any server, so now I'm trying do it manual. Is it ok?
Is there an update to 3.0 or have to install completely?