if there is no power in car battery. Nothing electric will work. get booster pack or jump leads to your cars battery and you should then have power for handbrake.
common fault on old Renaults like this ,the throttle position sensor inside the car ,change it .Don't ask me why but they lose power and will only idle but no faults show anywhere
There's a website that has all this information about all this and manuals everything totally free there are many actually but I personally like few . reliable-store
let me know if u need help
thanks