I mean I guess it depends how strictly you take it. If literally everything works out in your favour, and you set out to build it, you'll know you're done when you don't feel inclined to do anything further because it worked out.

As far as using/repairs etc, you obviously wouldn't attempt to do so during times the coin is not in effect, you'd just wait till the next heads. When you attempt to use it, it will work out.

But even that can be potentially mitigated somewhat. You could say, set out to write a manual that even a child could understand for example.

I think the best path though would be to use it to make money, then once you have effectively unlimited funds, create companies aimed towards goals you want to achieve, and use the 12 hours to set out to hire the best, smartest and most loyal people in the world. You'll be able to pay them whatever they need. Any time they get stuck, you can use the 12 hours to guide them.

12 hours every ~4 weeks might not seem like much, but if you use that time to set everything up well and prepare for the 12 hours, you'll get a lot done in that time. The only issue is people at your companies trying to work out why the super rich super genius that was able to start all these things only comes into work to help every couple of months.

You'd probably want to come across as super eccentric or something as well.

Sure - invent a time machine that ~~any idiot~~ only you can use without any special knowledge - interface is date here, push button or similar.

If it breaks? Wait 14 days on average.

When you can do anything, the only limit is your imagination. You're god with a cooldown, and even the cooldown quickly becomes trivial.

...You'd succeed at trying to commit something to memory permanently.

...You'd succeed at creating and moving to a perfect universe (or reshaping this one) in the space of 5 minutes.