PTT (= push-to-talk) is the talk button. As long as it remains pressed, the device transmits (radios). Release the key immediately after speaking so that the other party can answer. The short tone when pressing the key is only an acoustic signal that the key has been pressed and the unit is in transmitting mode. It may be possible to suppress it (--> operating instructions). I cannot understand the problem described above.

Yes

Everyone can talk and listen to everyone, provided they can set the same freq. This freq is simply saved as "channels" to facilitate operation. There are some with 8 or 10 or 40 channels depending on the manufacturer/ model. If the 40 is on a channel (i.e. freq) that yours is not, you will not hear each other. The 40 must then be set to one of the 8 channels of your model, then it works again. +++++++++++++++++++++++++++++++++++++++++++++++++ AM or FM the difference is in the transmitting power; Since a few years, FM or SSB can transmit 4 watts and AM 1 watt on 40 channels (in Switzerland). If you have a device that can do both, you can set FM with more transmitting power. You will then transmit with 4 watts. However, you may have poorer sound and the battery will run out. Everything has advantages and disadvantages. ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ These simple handheld radios usually have 0.5 watts of transmitting power, which of course reduces the range even more. Add to that a short antenna and you have a range of 0.5 to 5 km. (The 10 km described here are an illusion). This is also dependent on the weather (e.g. humidity), just as concrete or houses massively reduce it in the city. I use this one to work indoors. It's enough for that. It would also be OK on the ski slope.

It depends on when the product was delivered from the factory... Depending on how long the product has been lying around in a warehouse somewhere, it is normal that the battery has already lost some capacity. I don't quite see the problem if you can charge the product.

Everything is double, including batteries, charging cable, etc.

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