Hello vishwajeet :) !
You can use those assets commercially, yes ! They'll stay free, don't worry (I'll edit the description in this direction).
You can credit me by mentionning my name ("Gif") with a contact such as my itch page (Gif - itch.io) or my Twitter page (Gif (@gif_not_jif) / Twitter).
Anyway, you are 100% safe :D !