Devil May Cry 100% is a speedrun category in which the player tries to complete the game as fast as possible in addition to fully clearing the game. Glitches such as Shadow despawn are all allowed. Using other programs to affect the game or modifying the game with mod is not allowed.
The leaderboards for this category are available here
The objective is 100% game completion, meaning all significant interactions and criteria in each Missions needs to be performed and accomplished.
(1) All of them need to be cleared when you finish the game. The rewards you get from these missions are part of full health upgrade requirement, which is the Blue Orb Fragment.
(2) While Any% skips majority of firearms, this category requires all of them for full completion. The devilarms by default are mandatory progression pick.
(The rules here are specific to this category. Go to this page to find the rules that apply to all Devil May Cry speedruns.)
Learning a 100% category may seem daunting at first, but there are ways of making things easier. It's very important to know that each difficulty has significant route difference.
Once you have completed your first run and made savefiles practice the parts you are least confident with then try another run.