Can I sell my previously done work to employees on Fiverr if there is not copyright issue?
i don’t: know about that
I assume you mean, can you recycle work, and deliver it to multiple people? Let me ask you this instead: If you were a buyer, and you placed and order with a seller, would YOU want them to deliver work to you that they’re giving to multiple other people? Probably not. If a buyer hires you, they likely want original work. Don’t try to cheat your buyers, or cut corners to avoid doing the original work you are hired to complete.
Also if you read the TOS the work you deliver to the buyer belongs to the buyer. You cannot resell something that belongs to your buyer!