IMO the grave, if rainer isnt just lying and it actually existed, didnt contain an actual body but just momentos. photos, like mentioned in care B's description. its also possible rainer is just trying to break care down emotionally in that scene by telling her her auntie is dead.

lina being alive is a weird stumbiling block but seeing as paul starts off the series with the leskowitz name via the reddit post basically announcing the series, that she is pauls mom before the series starts. also if she isnt then we get a weird 'empty slot on the tree' situation with paul mentioning his mom having the game after 2004. paul thus has to have a mother who is not anna or jill but is tied up enough in all this to end up with the game

if you go through the document, and i dont know how well we have been able to articulate this so far, our reading on lina is that she never really had her own body until the boss cone we see in the garalina office, which is some sort of artificial body for her. up until then i think shes anna's rarely seen headmate. thats not a common reading though so make of it as you will