If my invention is not patented and then mass-produced in the market, can I sue for infringement?

Aiming at the first question: you can't engage in infringement if you flow out of the market through normal channels. There are several rules about the loss of novelty. Please refer to the review guide. As long as this product is circulated in the market, it already belongs to the existing technology, and the patent will not be approved in the applicant country. Even if you can apply, others can take this product to invalidate your patent, because the patent application time is later.

The second question: protect your own interests, apply for patents first, and then produce products. It doesn't cost much to apply for a patent, thousands of dollars, depending on which one you apply for, novelty, inventiveness, appearance and price are all different. This patent fee is very small, and the benefits after the patent is used for production are great.

The third question: patent protection is realized by applying for a patent.

The fourth question: Patent prosecution involves legal proceedings. Only know the patent, the specific cost is unknown.