the only advantage to shooting interlaced is interpooling (i think thats what its called?) where you seperate the shot into 50 half frames and animate the other halves in with AE, but you loose resolution. But as you can tell, i don't know much about interlaced because i only shoot progressive.
Interlaced footage is only half resolution as progressive footage. I honestly see zero reason why they still make cameras that shoot interlaced (unless it records to tape).
shooting 25p will look MUCH better, but you have to be more on top of your shit. Your pans have to match the movement of your subject almost perfectly if you don't want any strobing. It's hard, but it looks really good, so have at it!
30p is for NTSC as I understand it. so no, it doesn't it has a lower res setting that isn't true hd, can't remember what it is though. think it might be 720 / 25p. but yeah i think that's the difference between us limeys and you yanks!