youtube got teach how to disable alarm if keyless no battery, put it near the push start button after u enter the car
if car no battery, then change it first

one feature is use keyfob to enable car to start, if keyfob battery die

not sure what u mean by disable alarm manually, maybe if u mean without keyfob? is that like older cars without immobilizer keyfob, and have to press a special button while turning the key?

but did hear before, if myvi car battery die need to pair back to keyfob in case some memory loss - this one need SC liao