Is there a proper way to open a famicom cart without any special equipment? I've tried prying one cart with a plastic guitar pick-like prying tool, but managed to brake the tabs (luckily it wasn't a valuable game..)
Get a set of plastic iphone tools. The carts are 31 years old, expect the plastic tabs inside to break off. If you need to shim on one side whilst opening the other side (usually) I will use a soft bamboo sliver, usually carved off the disposable chopsticks I have too many of.