Hi. We are using it for 2nd time for ds. 1) I don't think so -I think that's only for moses baskets or slatted bases. We aren't using a board with solid base of crib. 2) yes you can switch both units off without needing a reset in my experience. What I find useful too is that if you just have the 'baby's' unit on it still work as a movement sensor and an alarm horses off if no movement (or more likely if you forget to turn it off when you take baby out! ). So you can monitor breathing when sleeping in the same room and not needing the sound aspect. 3) yes, the sound is supposed to only come on when it detects there is a sound. Otherwise you would be listening to static all the time. You can adjust the sensitivity if you think it isn't picking a all sounds.
1: Our cot has wooden slats, and we still used a hardboard. Not sure it's strictly necessary but I think the harder you can press the sensor mat against the mattress the more sensitive it will be
2: Yes, if you're using the breathing monitor you'll need to turn the nursery part off when you take him out of the bed, otherwise it'll alarm. No issue with turning both units off, they'll re-connect just fine when you turn them back on
3: The sound only transmits when something is making a sound, if that makes sense. If there are quiet noises then sometimes the transmission switches off then back on again. Try turning the volume up, that seems to help sometimes