When you start Extra Story, you will be presented with a Time Rift with either you current Mentor next to it, or someone else from the Time Nest. The Rift is part of the Time Patroller Path, the Path you choose to do first doesnt matter as you can simply repeat Extra Story once youve finished the ongoing one (ongoing Stories are marked with a blue-ish Story mission Icon over the Time Nest on the map).

Getting this Achievement is fairly simple, you just need to complete both Paths of Extra Story, those being Fu's Path and the Time Patroller Path. You cant get this Achievement through Tokipedia either so I recommend going through both Paths individually and if you have started an Extra Story and did the Missions on Fu's side and the Time Patroller side mixed(like i did at least) you just have to finish the Story, check Tokipedia for your missing Missions and then redo a Path. You might also consider taking the annoying/weaker mentors (Jaco or Hercule for example) first.

This is arguably the most Annoying Achievement in the game because you have to get the Tokipedia to 100% meaning you have to do every mission with all the shown Mentors, the 5th Mission requiring all 31 Mentors(at the time of release). This is a little simpler because you can use Tokipedia and just do the Missions over and over again, it just takes a really long time.

When doing the Fu part with Goku as a Mentor, the last mission will have an Alternate ending. Usually you will fight Goku in SSJB and he will be a somewhat difficult enemy if youre not prepared, but if you have Goku as a Mentor, he will fight using MUI afterwards and he will have a ton more HP than usually. This fight is very difficult if you dont know how to deal with MUI so a little tip I can give is use Ki Blast Attacks, he cant dodge them. Spam them all you like and shoot a Ki blast at Goku when he is using a Ultimate Attack to make him dodge and cancel it. Using this you can also Drain him of his Stamina but I dont recommend it because you wont break him unless you use Prelude to Destruction or the Whis Counterpart(i forgot the name)

Good Luck getting these done!