What are the requirements for US design application documents

yes. If the appearance of the designs embodying the same design concept is similar, the combined design may be submitted in one design application.

20 years

Reinstatement of the right of priority on the grounds of "unintentional" is accepted and subject to payment of the right of priority restoration fee.

no

If the disclosure is caused by the inventor or the information source of the discloser is the inventor; or if the disclosure occurs again after being disclosed by the above-mentioned subject, the patent enjoys a novelty grace period within 12 months before the filing date/priority date.

• Grant fee: The applicant shall pay the granted registration fee within 3 months after receiving the notification of granted decision.
• Annuity: Three annual fees shall be paid in the 3.5th year, 7.5 years and 11.5 years from the date of granted, and the payment may be postponed within 6 months after the overdue period, but 25% of the annual fee of the current year shall be paid at the same time as a penalty.

• via Paris Convention : 6 months from earliest priority date.
• Hague Agreement route: 6 months from earliest priority date.

yes

2-3 years