Obviously it's well past 12 weeks but I thought I'd share goals that I've reached since the challenge has been issued:
Weighted Pistol Squat: still working on un-weighted pistol squat.
Handstand Pushups: can do reps now.
Bodysaw Pushups: this is a variation of the one-armed pushup.
Airborne Lunges: another variation of the one-legged squat, can do 10 reps.
Weighted Pullups: can do these wearing forty-pound weight vest.
Back-Bridge: some days are still better than others.
Lever Rows: like inverted rows but with feet in air.
Barbell Deadlift: have gotten 1.8 X bodyweight and am gradually working towards double.
Squat Jumps with Mountain Climbers 15, 14, 13 ... 1: under 5:00.
Bag Carry: 10 trips across backyard without dropping.
And mobility has improved overall. I can do certain movements I haven't done in years, if ever. Hamstrings are still stiff but have improved marginally.