Is the platinum possible in one playthrough?

[Kishnabe]

Read that a few people have got this in one play through and key saves. Every guide, and mostly everyone got this in 2+ play through.

 

Can't you just save at key areas before some EX icons and before the final mission.

 

Load up your clear save and those saves...and easily get all 20 EX missions and Frames?

 

Lowering rank...how many saves you made count or how many save slots you used?

[Thoazol]

If the only trigger for NG+ stuff is the clear save, then yeah. 1 and some fraction of a play-through is enough provided it spawns you with enough sub-weapons to reach them.

 

Lowering rank with saves though. I don't have a credible source, but from what I read you'd need dozens of saves to knock it down a rank, and depending on your other stats it can be an unreliable method. If you're intent on lowering your rank through anything, get a few continues against the final boss, or a second run with A ranks on both rescue missions.