1. In its general meaning,
reverend means 'deserving reverence', and is most often found in clerical contexts even when it is not a formal title, whereas
reverent means 'showing reverence' in wider contexts:
He also formed close links with the network of local Puritan ministers...whom he described in his will as 'my reverend and pious friends'—Dictionary of National Biography, 1993
You can get away from the reverent hush of the concert hall—Times, 2005.
Reverential means 'characterized by reverence', and the main difference in meaning between it and
reverent is that
reverent describes a feeling or attitude and is judgemental whereas
reverential denotes a connection with
reverence and is informational:
When she walked into a village the Africans would often clap their hands in a reverential way—W. Green, 1988.
2. Reverend, abbreviated
Revd (no full stop) or
Rev., is most commonly found as a title applied to certain members of the clergy.