Optima gen4 panel question

Recently posted question about new bellbox wiring to old mx6 panel, thanks Rulland for great advice. Bell works great but problem still persists ( zone 4 - magnetic door contacts - going off, replaced contacts ) new batt fitted to old panel.
I have decided to replace mx6 with optima 8ep396A , upon reading engineering manual I have 2 questions,
1- PA user reset- factory set to NO. I want it set so if Attack button is pressed I can reset with customer code so do I need it set to ON or OFF ?
2- TIMERS Bell time factory set at 15 min, to change to 20 min manual says press 2 then 0 which makes sense,so if I want alarm set for 3 min ( I've upset neighbors enough with false alarms, they don't need 15 min ) common sense says press 0 then 3 but not sure if 15 min is minimum, can anyone advise.
Also, have read mx6 and optima 8ep396A are straightforward swop of cables is this correct.
Many thanks, John