Can someone help me spec a system?

I have an old paradox system I want to change over to Konnected. I have a 4 year old starting to open doors and I am worried he will walk out while we are asleep. Below are the specs

3 doors
15 windows
5 Hardwired smoke detectors
1 siren (siren removed but wires remain)

-Can someone recommend the correct system that integrates everything above?
-I don’t know if the smoke detectors are tied to the old alarm or how to check. Any advice?
-I need to buy a new siren. Recommendations?
-I want to be able to hear or trigger something if a door/window is opened.


Sorry it bunched up my post. I also want to use the backup battery if possible.