God so loved the world...The word 'world' does not mean 'everybody whoever lived'.
If you were of the world, the world would love its own; but because you are not of the world, but I chose you out of the world, because of this the world hates you.[John 15:19]
The Father has chosen His elect sheep from the world. They are no longer of the world, but were chosen out of it. It also says the world hates us, the believers. So just in this one verse alone, the word 'world' can not mean 'everybody whoever lived', but rather it means all over the world.
I know that the Greek word κόσμος does not always mean "the entire human race". However, contextually, John 3:16 does, as it is the only way that this word used here can be understood. The leading Greek scholars are in agreement that κόσμος here means the "entire human race", as did John Calvin.
J H Thayer:
“the inhabitants of the earth, men,
the human race. Jn. i.10, 29, iii.16sq”
W F Arndt and F W Gingrich:
“
of all mankind, but especially of believers as objects of God’s love”
J Parkhurst:
“the world, i.e., the
whole race of mankind, both believers and unbelievers, both good and bad.”
E Robinson:
“the world for the
inhabitants of the earth, men,
mankind. John.1.29, 3:16”
Hermann Cremer:
“It denotes the ordered
entirety of God’s creation, humanity itself”
The NIV Theological Dictionary of New Testament Words:
“in Jn. kosmos almost always denotes
the world of humans, esp. the
world of sinful humanity that opposes God, resists the redeeming work of the Son, does not believe in Him”
G Kittel and G Friedrich:
“All the meanings of kosmos come together in the usage of the Fourth Gospel. Not just the Prologue uses kosmos for
the world in the sense of the universe”
W E Vine:
“the
human race,
mankind”
A T Robertson:
The world (ton kosmon). The
whole cosmos of men, including Gentiles, the
whole human race. This
universal aspect of God's love appears also in 2Co 5:19; Rom 5:8”
M Vincent:
“The
sum-total of humanity in the world; the
human race”
John Calvin
"
the whole human race...all men without exception"
This is what Robert Dabney, who was Refromed, says about κόσμος, in John 3:16
"In John iii.16, make '
the world' which Christ loved, to mean '
the elect world', and we reach the absurdity, that some of the elect may not believe, and perish" (Systematic Theology, p.525)
Another Reformed commentary, by Jamieson. Fausset and Brown, on the use of "whole world" in 1 John 2:2, says,
"Also for the sins of the whole world. Christ's advocacy is limited to believers (1Jn_2:1; 1Jn_1:7):
His propitiation extends as widely as sin: note, 2Pe_2:1, "
the whole world"
cannot be restricted to the believing portion (cf. 1Jn_4:14 and 1Jn_5:19). '
Thou, too, art part of the world: thine heart cannot think, The Lord died for Peter and Paul, but not for me' (Luther)."
Word meanings and use must be determined by its context, and it is abundantly clear, even to Reformed teachers, that in John 3:16, κόσμος means the "entire human race", from Adam till the last person.