Bypass doors installation

I'm looking at replacing the old exterior door of my house with one that comes prehung and looking at my old door frame i started to wonder if i would have to remove my screen door as well to install the new exterior door? It looks like they share the same jamb , but without starting to strip it down i can't tell. Would i have to remove the exterior screen door as well to install the new insulated steel exterior door?? I hope that what i've written makes sense. Thanks Gord

Could anyone plz tell me if I understand this correctly? When inserting an inside door to a house, say to a bedroom, one that has a lock on the outside that takes a key, when installing the handles, isnt there a certain plate type thing that could be placed somewhere to make it so that while the door is locked, someone wont be able to just walk up to it with a butterknife and push the lock so that the door swings open!?!?! I am only asking because Im not sure and my younger sister wont stop entering my bedroom while im gone and have it locked, it's driving me nutts and rather than getting so angry as to where I hurt her cause I've had enough, I figure the more smart thing for me to do is fix it so that she just isnt able to successfully enter without permission. I just dont know what the plate thing looks like out of all the different types of plate type things that come with new handles. Can anyone explain to me what it looks like and where it goes plz, and thank you so very much