Questions about why God the Father required a sacrifice (and whether Jesus’ short-term death was really a sacrifice), whether Jesus’ disciples ever offered sacrifices at the temple, and what it means to say that sin causes separation from God if God is omnipresent.

Why did God the Father require a sacrifice, and if Jesus knew he would rise again in three days, was his death really a sacrifice?

Did Jesus’ disciples ever offer sacrifices at the temple, and if not, why not?

How can I explain the idea that “sin causes separation from God” to someone who believes that it denies God’s omnipresence and denies Jesus interacted with sinners?