Using the words like 'lept, crept, swept, hung' instead of 'leaped, creeped, sweeped and hanged' ?

I am not sure in terms of what is grammatically correct, but I was also taught crept, lept [I might be more inclined to say leapt though] and swept. Not only that but the others just sound wrong. The rules change all the time, like in some America I think they no longer use double letters with "ed" or "ing" as far as I know.

Leapt or leaped, crept but not creeped, swept but not sweeped. Hung is correct for normal uses; hanged means executed by hanging (...hanged by the neck until dead). Shined or shone. Lighted or lit.

IMO the ...t formations sound better than the others.

I think it's just a matter of language usage changing. I also learned swept and hung (but not leapt or crept), but either usage is considered correct. Hung, in particular, seems to be falling out of usage, although many people still use it. That may be due to the vulgar usage of "hung" being used for male genitality, so people switched to "hanged" when they are referring to hanging decorations or a suicide victim who has hung/hanged himself.

regularization of some irregular word forms is an ongoing process. spilt and spilled would be another older example. dreamed and dreamt. Some can have both ed and irregular forms for different tense uses. personally, I use leaped and creeped but still use swept and hung, although a person would be hanged, a thing would be hung (clothes are hung out to dry).

that is the thing about language and word use, it is always in evolution.

I am guessing swept