How do i prevent user from doing sales order to a Prospect. We want only certains users to allow the ability to convert prospect to lead/Client via status modification

A workflow with the Return User Error action for that specific user role, and that specific prospect?

It could work, will try, thanks

But of course, if someone else creates a SO against that prospect and converts that prospect to a customer, then your original user still wont be able to create a SO for that now customer (or use condition = {name of entity} AND stage = prospect)

Yes, to avoid that problem i was thinking in a script that check the value of a checkbox field in the client form. That field, will change its value depending if certains fields have value inside. If the checkbox = true, then u can do the SO. If it is false, then when you select the Prospect in the SO, it will show a alert message, saying that u cant do a SO to that Prospect, and it will show the same message every time u try to save the SO. A little intricated, but it will be automatic, and i dont have to specify roles or users.