Off topic = is it possible to become a United States army general at the age of 30.

Army promotions are controlled by time in service (TIS) and time in grade (TIG). Time in service is the total accumulated military service and time in grade is the amount of service in the current paygrade. For officers, TIG requirements are set by federal law (United States Code: Title 10) while TIS can fluctuate based on needs of the Army.

General officers are known as Flag Officers. Promotion to Flag Officer is extremely competitive with less than 1 percent of career officers ever advancing to become a Flag Officer.
The President of the United States nominates General officers with confirmation by the Senate. To help facilitate the process, the Army holds promotion boards to recommend officers for promotion to O-7 to O-10. As there are set limits for the general officer ranks, vacancies usually occur only when a general officer gets promoted or retires. When that happens, the President nominates officers for promotion from the list of recommendations provided by the Army (with advice from the Secretary of Defense, Secretary of the Army, and the Army Chief of Staff.