Salvation is a gift from God. One can receive it but reject it later. Just as Paul told us.
"Work out your salvation with fear and trembling" (Philippians 2:12).
Right. It is a gift from God. Again, though, if you can lose such a gift, that implies that you can earn keeping such a gift. Your good works garner sufficient favor from the Lord that He continues allowing you to keep that gift.
And that’s not good news, that Christ’s sacrifice is insufficient to cover all our sins.
To be honest, I don’t understand the point of this discussion. Those who belong to the Lord yearn to serve Him anyway, regardless of whether it’s in response to His love or in vain effort to earn His love.