Can I sell things that others have applied for patents? Will a small matter infringe upon rights? Master guidance!

Many domestic patents, especially utility models, have very small claims and are easy to evade. If you use them directly, and that patent is in the right state, it must be infringement. Playing small games doesn't necessarily care. Once it gets bigger, it will be very dangerous and often not worth the loss. Beware of the trap of "fattening before killing"