Magsafe 2 plug sparked when putting in socket, burned 3 prong plug and now doesn't work

A short circuit would cause the problem you have had. It is not necessarily the Magsafe but if you have fixed the house fuses and the mains sockets are now all working again, try a simple hair dryer in the socket that got burned. If the hair dryer works, then that side is clear.

Take both the MBAir and the Magsafe back to an Apple store for testing. After 4 years you would not get a free replacement for the Magsafe. You do need to check out the machine too, though again, it is too late for free replacements.

Then get a qualified electrician to examine and repair the mains plug before anything. Let us know what happens at the store. Make an appointment before you go, the stores get very busy. Happy to have helped.