In today's data-driven world, ensuring clean and accurate data is paramount. With PowerFx, you can take data validation to the next level in PowerApps Applications using the Regex Expressions in combination with functions like CountIf, IsMatch, Split, and Not. What's even cooler? This code is user-interactive, allowing your users to spot and correct data errors effortlessly without the need for any Variable or Collection 
This can be combined with multiple text inputs with a sum function to check for each. 

A use case scenario here - https://medium.com/@olumideojoniyi/data-input-validation-in-powerapps-fd7e0b9b2db7

We will create a sample approval process in this chapter which will give an overview of how you can create your own approval processes in your business. We will first create a SharePoint list.