1. Whether it is necessary depends on you personally. I think it is still necessary. The agency fee will still be collected
2. If you apply at the same time, there will be no priority. If you apply for a utility model first and then apply for an invention, you can claim priority within 12 months. But when you claim priority, you must also give up the prior utility model patent, otherwise the invention cannot be authorized.
3. Yes
4. It is easy to apply if you apply personally. Download the fee reduction request form on the website of the State Intellectual Property Office, fill it out, and ask your unit or street to issue an income certificate. Write your income as low as possible