can I return an item purchase if I don't have sales slip?

Yup

Yes

Yes but only get in store credit

If you don't have a receipt, you will have to show your ID and they put the money on a gift card for Walmart

You should be able to but will more than likely get an in store credit

I honestly don't know. If they do my neighbor said you would get in store credit. You won't get your money back