Are the previous prayers invalid due to performing ablution in the manner mentioned, and what must be done now?

Wiping over socks requires the same conditions as wiping over leather slippers (khuffayn). The most important of these is that the socks must be thick, so that no part of the foot is visible through them, and they must be durable enough to walk in continuously.

Scholars have differed regarding the ruling on wearing socks when one's ritual purity (tahara) is incomplete. The majority of scholars stipulate that one must wear them while in a state of complete purity for wiping over them to be valid. However, the Hanafis permit this, reasoning that wiping was legislated out of necessity, and this necessity arises at the time of ritual impurity (hadath).

Accordingly, if you wiped over your socks after putting them on while your purity was incomplete, then according to the majority opinion, the wiping is invalid, and you must repeat all prayers performed with that ablution. However, according to the Hanafis, the wiping is valid, and you are not required to repeat the prayers. You may adopt the Hanafi view, especially if you did so out of ignorance.