Hello Lauvoothef40
You are asking questions that have been answered before. I suggest reading some of the previous posts, and you will know a lot about Swiss public transport.
For the child, you need the Swiss Family Card. This is complemtary when you purchase the Swiss Half Fare Card, yet you must request it (enter the child as well when you are about to purchase the Swiss Family Card).
With the Swiss Family Card, the child travels for free on almost all public transport services; there are a few exceptions for cable cars and gondolas, which are operated by private owners. You can find out from the operator’s website if they accept the Swiss Family Card, which equals the Junior Card in terms of validity.
Kind regards,
Roland