God gave angels and humans free will, given by the permissive will of God, therefore the Catechism No. 1861 states “for our freedom has the power to make choices for ever, with no turning back.” This occurs whenever sanctifying grace is lost and not repented and forgiven prior to death with the immediate particular judgement. The chief punishment of hell is never having the Beatific Vision, about which the Catechism No. 1028 states “God cannot be seen as he is, unless he himself opens up his mystery to man’s immediate contemplation and gives him the capacity for it. The Church calls this contemplation of God in his heavenly glory “the beatific vision””. It must therefore be a divine law.
This is why we have confession. All sins are against God. We confess to say we are sorry for rejecting God’s love in preference to sinning. We will try not to sin again. We are human and will sin again . That is why we have the sacrament of confession.
Umm… I’d haggle you with that one. God shows eternal love to all – even those who reject him – and justice to all – even those who accept Him. It’s both/and, not either/or.
In the context of the question (eternity), the answer comes down to “final judgment”. So… if you were to sin mortally against God and not repent, then His justice would demand the consequences of eternal damnation. That would, coincidentally, be an expression of His love: He would not force you into an eternity you did not choose.