The implication from the art we are shown from history is they burned the casing. So it seems the mutant escaped the casing and they then cut up the creature as they perceived it to be flameproof if it survived the burning of the conveyance.
It’s said a few times that the Dalek was one of the first to leave Skaro, so I think it’s fair to assume it is a pre-Time War Dalek. (I think I mentioned upthread that I’m surprised they didn’t make this Dalek the one responsible for the Dalek Invasiton of the Earth.) What complicates this is that it cobbles together it’s new casing from scrap metal and pieces of the Time War-era Dalek from the Black Archive.
It’s said a few times that the Dalek was one of the first to leave Skaro, so I think it’s fair to assume it is a pre-Time War Dalek. (I think I mentioned upthread that I’m surprised they didn’t make this Dalek the one responsible for the Dalek Invasiton of the Earth.) What complicates this is that it cobbles together it’s new casing from scrap metal and pieces of the Time War-era Dalek from the Black Archive.