The hike seems doable provided FR201 is snow free, and I'd think it would be snow free by now. But I think it's longer than 12 miles - maybe more like 16.5-17.5
Not sure about the entire length of FR25 - FR25 should be good to the intersection of FR25/FR25A. From there - on FR25A you may want to walk part of FR25A, it gets gnarly the last 2 miles. Haven't driven from that spot any further along FR25 towards mormon grove myself.
Don't know what a Forerunner is, but a 4Runner will easily make it to Peeley TH and make it to the part of FR25A where it gets really bad.