SD GUNDAM BATTLE ALLIANCE

This is the first Directory that won't be a straightforward fix, as you'll be required to go back to Directory 3 to complete the True Mission there, which is a pain, bring high level partners to help you. The reason for it, is that you need to "rescue" the pilots from Iron Blooded Orphans from different missions across Directory 4 before the final True Mission will be made available in Directory 3. After that, you'll get another boss battle to finish off Directory 4.

This may also be the first Directory where you might need to spend time replaying previous missions to level up your partners to boost their effectiveness in combat, unless you spent the entire game using the same partners to max out their Friendship and level them up like I did, I had to replay the last True Mission of Directory 3 with my maxed out Kai and Hayato.

And in case you missed it in the tutorial section, left and right on the D-Pad will command your respective partners to use their ultimate ability against your currently selected target.