The aorist tense, gave. So Rev. The reference is to the historic fact of the gift. So 1Jo 3:23 : “We should love one another as He gave (ἔδωκεν) us commandment.” 1Jo 3:24 : “We know that He abideth in us by the Spirit which He gave (ἔδωκεν) us.” On the other hand, 1Jo 3:1 : “Behold what manner of love the Father hath bestowed (δέδωκεν) upon us.” The gift of love abides in the fact that we are now children of God (1Jo 3:2).
Eternal life (ζωὴν αἰώνιον)
Compare the phrase τὴν ζωὴν τὴν αἰώνιον the life, the eternal life (1Jo 1:2), and ἡ αἰώνιος ζωὴ the eternal life (Joh 17:3). For the distinction between the phrases see on 1Jo 1:2. The phrase here, without either article, merely defines the character of the life.