Hi Emmanuel,

You'll want this message to always appear on the page while the request is in a specific status/step, as you want users to still view it if they come back to the request later after initially transition to that step.

My advice would thus be to create a field containing Text Area with validation type of "Constant rendered HTML", which lets you write a constant value with abritrary HTML/CSS/JS in a PPM field, which will be rendered on the page - so you can put formatting, links, and even interactions with some JS code.

As for enforcing all the requirements, you can use UI rules to set fields Required. If you really want to go into the weeds you can even register a click handler on the next step button from your custom HTML field and run your own custom JS code to do validation before allowing the button to be clicked - but this is highly custom code if you start to manipulate the PPM DOM and register custom JS event Handlers on the page components - better stick to UI Rules & SQL Rules if that's an option.