Hello, now I will answer your questions one by one:
1. Regarding handling patent applications on behalf of the applicant, the applicant can issue a power of attorney and sign it. The trustee only needs to bring his/her identity documents and the certificates of the trustee.
2. It doesn’t matter whether you apply individually or jointly. When you implement the patent in the future, you just need to submit a request for an implementation license to the State Intellectual Property Office.
3. The validity period is calculated from the date of application. It is 20 years for inventions and 10 years for newness and appearance. It has no protective effect without authorization.
4. Prosecution can be entrusted.