If you pick the reserves, then you can do as you please since you are a part time Marine and it is not like being on active duty.
Reserve duty means you are a part time Marine. Once you graduate boot camp and your schooling, you go back home and you report to your duty center one weekend a month and two weeks during the summer.
Reserve Marines can be activated at any time which means you become active duty until you are done with your mission. This can be up to one full year. And as a reserve Marine you get paid less since you are a part timer. And you only get benefits/medical/dental when you are doing your weekend warrior thing, or when activated. You CAN NOT go from active duty to reserve while on active duty unless you are leaving active duty.
You can go from reserve to active duty only if you are allowed to by your command, and you may lose your job and bonuses since you are asking for a new contract. Your command does not have to let you do this move, and it can take as little as a few months, or as long as a year or two.
If you are 100 percent sure that you want to become an officer, then you enroll into college and do the PLC program or OCS program, or you try the NROTC program. Enlisting into the reserves to earn your degree so you then can hop on over to the officer side of the USMC is NOT a good idea. It may sound like a simple idea, but stuff happens. If you are activated while in the reserves, you lose one full year from school, so now your four year degree will be bumped to a five year degree assuming you are on track. And if you get into trouble during this time and ruin your chance of becoming an officer.
The money you get while in the reserves is not a lot since you are a reservist. Don’t be suckered into enlisting first if you truly want to become an officer. Your college is NOT paid for just because you join the reserves. You must serve in the reserves for a while to earn any money for college.