Are punctures in the sidewall repairable?
In a word, no. More specifically, a puncture that falls outside the minor repair area is not eligible for fixing because of its proximity to the sidewall.
The sidewall is off limits for a straightforward reason. When the tyre is in daily operation, this section undergoes a significant amount of stress. Any attempts at making repairs in this area will potentially weaken the structural integrity of the tyre.
Another factor is that the sidewall experiences the most flex in the tyre. It’s unlikely that a repair patch applied here will stay in place for very long, and the tyre will fail once again.
One more thing concerning the sidewall is that you should avoid driving any further on a flat tyre if you hope to salvage it. Inflation pressure maintains the shape of the tyre while driving; when that pressure is lost, the tyre sidewall is going to be pinched between the wheel rim and the road, so continuing to drive will extend the damage beyond the minor repair area.
In other words, do not drive on a deflated tyre while the puncture is within the minor repair area (and is therefore repairable). The tyre sidewall could sustain additional damage that renders it beyond repair. The better course of action is to have the vehicle towed or swap the punctured tyre out for the spare tyre until you reach the nearest garage.