OK, so I have a little difficulty with the concept of apostles being resurrected? I always thought that they transformed into apostles to keep living. Technically they were not dead, but in coma or a deep spiritual trance, or so I thought.
Or am I missing something?
At the moment it doesn't look like it's possible, through a normal behelit. When the slug count was going to get killed by Guts, his blood activated the behelit that opened the God Hand's dimension, where they gathered. They told him if he wanted to get their help, he would have to sacrifice Theresia, his daughter, the only thing dear to him (he sacrificed his wife the first time). He refused and got sucked into the vortex of souls. I do not think the apostles can be given another form(reincarnation) after the first time, simply because the form they take is supposed to represent who they truly are, their ideal form. We saw that with Griffith.
The case with Ganishka is different, his original form what that of a mist. When he confronted Griffith the latter dispersed him, because he's just mist. Ganishka unlike the other apostles didn't want to serve Griffith, so he looked to get stronger. That's why Daiba created the man-made behelit that is able to transform new borns into demon children. It worked differently than the regular behelit, since it allowed spirits to inhabit human bodies.It's not like the normal behelit where the apostle needs to sacrifice what is dear to him.
When he fused with the man-made behelit he took on the form commonly know as Shiva,this time around he was solid, not a mist. He also lost his conscioussness, perhaps because the behelit was incomplete. But it seems that the behelit allowed the merging of layers, it was most likely a key to access the different planes, and when SK destroyed it by accident the merging of layers happened.
There is no indication that a normal behelit allows an apostle to be reincarnated a second time, with a different form. It's mostly a tool to contact the God hand, who then can save the apostle's life, in exchange of him doing another sacrifice.