Yet the Torah says it is a sin for a "ger" to eat nevelah:
"And every soul that eateth that which died [of itself,] or that which was torn [with beasts, whether it be] one of your own country, or a stranger, he shall both wash his clothes, and bathe [himself] in water, and be unclean until the even: then shall he be clean. But if he wash [them] not, nor bathe his flesh; then he shall bear his iniquity," (Leviticus 17:15-16)
Yet the Torah also says it's okay for an Israelite to give nevelah to a "ger"!
"Ye shall not eat [of] any thing that dieth of itself: thou shalt give it unto the stranger that [is] in thy gates, that he may eat it; or thou mayest sell it unto an alien: for thou [art] an holy people unto the LORD thy God. Thou shalt not seethe a kid in his mother’s milk," (Deuteronomy 14:21)Oh, dear! How do we resolve this contradiction?
Well, the authoritative men who composed the Septuagint explained that there were different classes of ger. These learned men used the term "paroikos" (one who sojourns but has no political rights) to translate ger in those passages where the ger could not logically have been a covenant member; they used "proselutos" to translate ger where the ger must logically have been a covenant member.
So how did a ger transition to the proselutos status?
The only thing we know is that Exodus 12:48 says that a ger is just a regular old ger until he observes Passover. Once he observes Passover then he is "like" an ezrach. And, yes, he had to become circumcised to be able to observe the Passover and become like an ezrach.
Anyway, that's how it was apparently done in the old days (and hey I could be wrong! feel free to challenge me if you have another opinion).
It's more important to understand how it works today:
Now that Yeshua has become our Passover Lamb--all who believe in Him are welcomed into the covenantal family. His blood somehow (don't ask me how exactly) becomes your blood. He becomes your father. Now that's the "substance" behind the "shadow" of Passover. We should still keep in mind that the earthly shadow is governed by Torah. And Torah says you have to literally (not metaphorically) become circumcised in order to partake of the lamb sacrifice during an actual Passover. But this won't even be an issue until Yeshua comes back and restores the Temple.
NOTE: I won't be able to respond to comments here until tomorrow around 2PM. Shalom!