Disable approval option form the dropdown in workflow form

On the workflow im creating i need to disable the approval option from the dropdown. The concept is that if the checklist is not fully completed, the approver can t approve the operation. 

I have in the dropdown the following options: 

Approve

Aprove with restrictions

Reject

I need that if checklist is not completed, the approve can only choose aprove with restrictions or reject. 

Is it possible?

You can use the condition Enable/Require Field base on other field on the form.

User guide: How to Enable/Disable Fields Using Conditional Logic

In your case, you can use this Condition to disable the Dropdown field when approval logic is not true.

I hope this help. Let us know if you need further assistance.

Thanks, the disable button is not as an option. Can i disable the submit button?

Can you please reiterate your previous response. It is a bit unclear how you meant.

We can give you a more appropriate suggestion if we have a better understanding of the requirements. 

Can i disable the submit button?

If you meant using Condition logic also, the answer is Yes. The Enable/Require condition is applicable to the form Submit button as well.