I imagine you are talking about 737.
1. TE flaps are extended electrically in alternate configuration, LE flaps & slats hydraulically using standby system. As far as I know, PTU is only used for autoslats (but even for this you need fluid in system B), so when you have complete loss of hydraulic system B, you cannot retract LE devices after they are extended.
2. In dual engine failure situation, you need the thrust NOW. With an in-flight start of a single engine, priority is to monitor that engine starts normally (EGT, vibration, etc.) and to shut it down if abnormal start occurs.