1, with the same principle but different structure, can apply for different patents, and can apply for different patents according to the increase or decrease of technical characteristics, that is to say, you can apply for different patents as long as you improve.
2. The utility model patent does not conduct substantive examination when it is examined. As long as the law does not prohibit it and the format meets the requirements, it can generally be authorized. Therefore, the use of new patents may duplicate existing patents, resulting in the situation you mentioned.
Utility model patents may be repeatedly authorized, mainly relying on public supervision. If there are duplicate patents for the same technology, anyone can file an invalid application for the later patent, and the patent reexamination board will revoke the applicant's patent right after examination and verification.