There are 300 optional missions in Crisis Core Final Fantasy VII: Reunion. The Training Missions sub-category (M1-1) can be found in the Shinra Electric Power Company Category.
Shinra Power Electric Company: M1-1 Missions
The first mission in this sub-category is actually the first one you will unlock at the start of Chapter 1. You’ll have to wait until Chapter 9, however, to unlock any more of these missions.
As you may expect, these are training themed and all of these missions will have you fighting against various forms of Shinra Troopers. The last few missions in this sub-category will have you against massive odds so be sure you have ways to heal yourself and restore your AP and MP.
|1-1-1: Shinra’s Basic Training||During the story at the start of Chapter 1||Sentry (8)||Elixir|
|1-1-2: Shinra’s Advanced Training||At the start of Chapter 9||Alert Head, Captain, Grenade Combatant (2), Gun Bull Head (2)||Hero Drink|
|1-1-3: 50 Shinra Troopers||Complete Mission 1-1-2||Chief Petty Officer (45), Sergeant (5)||Hero Drink (2)|
|1-1-4: 100 Shinra Troopers||Complete Mission 1-1-3||Special Ops Officer (90), Sergeant Major (10)||Black Belt|
|1-1-5: 200 Shinra Troopers||Complete Mission 1-1-4||Combatant (180), Warrant Officer (20)||HP Up++ Materia|
|1-1-6: 1,000 Shinra Troopers||Complete Mission 1-1-5||Guard (900), Ensign (100)||Mug Materia|
None of the missions here bear special mention as their main difficulty comes from the sheer number of enemies you face in the later missions. For example, the Ensigns and Guards in M1-1-6 are only around Level 30 but the damage will add up over time. With this in mind, make sure you have plenty of restoratives at hand and then focus on using attacks and Materia that will hit a wide area when it comes to the later missions.
If you’re fortunate enough, you’ll get some of the more useful Limit Breaks and Summons. If you do, hold on to them for moments when there are as many enemies out as possible so that you can take them down in one fell swoop.
As for rewards, the HP Up++ Materia is great for maxing out your HP as it can eventually increase your HP by 150% at Master rank. The Black Belt is a useful accessory, it will increase your ATK and VIT by 20 while also offering resistance against Poison and Curse making it a good all around accessory.