You can be sponsored only by the organizations mentioned in the sponsorship list. Moreover, being a Christian is not enough and even Catholics are treated equally to non-Christians when applying. From what I know, CMC is run by a group of churches and if you apply via one of these, you have a good chance of getting sponsored.
The truth is these are just formal guidelines and to be sponsored all you need is genuine passion to serve the community. If you are passionate about social service your grades and even religion won't be a hindrance in your path. I have seen many exceptional cases, so what stops you from becoming one?