I have received several questions about the use of "whoever" in the translation of John 3:16, so I thought it would be good to clarify at least one thing.
Correct, the indefinite relative pronoun ὅστις does not occur in John 3:16, but language is not so monolithic that there is only one way to say something. In fact, whenever a commentary argues that if the author had meant to say one thing, he would have said it "this way," you should be suspicious. That's a naive approach to language.
However, we do have an indefinite construction in John 3:16 with the use of πᾶς and an articular imperfective participle (πᾶς ἡ πιστευών) used to indicate a generic, "general utterance" (see Wallace, 615f.). Just do a search for that construction and you can see it is universal in intent.
For example, "But I say to you that whoever looks at (πᾶς ὁ βλέπων) a woman to lust after her has already committed adultery with her in his heart" (Matt 5:28). Isn't Jesus saying this is a generic statement, true of all who look with the intent of lusting? Of course it is.
Interestingly, v 28 is followed by v 32 that uses another explicitly indefinite contraction. "But I say to you that anyone who divorces (ὃς ἂν ἀπολύσῃ) his wife, except on the ground of sexual immorality, makes her commit adultery" (Matt 5:32). ὃς ἄν is explicitly indefinite and general.