A: Just as God is no respecter of persons, neither is God respecter of earthly religions--there's none that's "better" in God's eyes than another. Whichever religious sect is most meaningful to you, or none at all, should be perfectly fine.
I presume by "soul" you're meaning "person"--the soul is the transportation vehicle to the mansion worlds for the personality and life experiences of the person who has died and has no relationship to science or history, which are mindal activities. What's important to make it "to the higher realms" is spiritual development through spirit-led decisions as a mortal. The faintest flicker of faith is all that's really required for a soul to reach those higher realms after death.
And yes, certainly the relatives or acquaintances or even complete strangers can pray for those who've departed. It won't move them along any faster, for again since God is no respecter of persons... either those who are prayed after or those who are not. It's the decision of the angels how rapidly one is moved from the sleeping survivor condition to incarnation on mansion world number one--the length of time between death and resurrection is of no real consequence. Sleeping survivors are generally resurrected as a group at the end of an age, or at a dispensational roll-call, such as occurred following the resurrection of Jesus from the tomb. He took a great many souls to heaven all at once.
Best wishes, and thank you for your question. I hope that the reply has been meaningful."