“What are the reasons bread and wine are used in the Eucharist?”

At Mass, the source of our salvation (Christ’s sacrifice on Calvary) is made present to us; Mass also unites us with the liturgy in heaven.

Do we receive Christ's pre-crucifixion body, his crucified body or his resurrected body?

The Catholic Church’s approach comes down to a desire for integrity and truthfulness. Holy Communion should always indicate a true unity.

How long does the unique, sacramental presence of the resurrected Christ remain with us?

Do we “miss out” on anything if we only receive a Host in Holy Communion?

This doctrine is not against reason, it is above reason; it’s a truth that had to be divinely revealed.