Christ is the firstfruits, but those verses do not say that he had to be resurrected on the day of Firstfruits.
*face palm* Yes it does, for Paul is referring to OT texts, and appying to Christ Jesus, by inspiration of the Holy Ghost, who also inspired the OT texts.
Gen 4:4 And Abel, he also brought of the firstlings of his flock and of the fat thereof. And the LORD had respect unto Abel and to his offering:
Joh_1:29 The next day John seeth Jesus coming unto him, and saith, Behold the Lamb of God, which taketh away the sin of the world.
Joh_1:36 And looking upon Jesus as he walked, he saith, Behold the Lamb of God!
Joh_5:39 Search the scriptures; for in them ye think ye have eternal life: and they are they which testify of me.
Jer_2:3 Israel was holiness unto the LORD, and the firstfruits of his increase: all that devour him shall offend; evil shall come upon them, saith the LORD.
Hos 11:1 When Israel was a child, then I loved him, and called my son out of Egypt. (Matthew 2:13-15,19-21; Jesus is the real Israel)
Eze_48:14 And they shall not sell of it, neither exchange, nor alienate the firstfruits of the land: for it is holy unto the LORD.
Act_4:27 For of a truth against thy holy child Jesus, whom thou hast anointed, both Herod, and Pontius Pilate, with the Gentiles, and the people of Israel, were gathered together,
Act_4:30 By stretching forth thine hand to heal; and that signs and wonders may be done by the name of thy holy child Jesus.