When I run it with your last code, it kept running prompt "X IS BAD" although it was "x is good" inside the downloaded email. I think I didn't code well in Parse/ElseIf so I changed PARSE EMAIL MESSAGE for REGEXP MATCH and got it working (I saw a previous example of yours you could find/match a text with regExpMatch) Thanks for the help.
My last questions

1) Does RegExpMatch process time is the same as ParseEmailMessage?
2) Is it possible to prompt the alert window "X IS BAD" to a specific time? Instead of running the action immediately after finding "x is bad", run it at 00s for example from the next minute.
3) Better 1 task or 2 tasks? So I want to find emails with subject "x" and "y" and that contain "x/y is bad" or "x/y is good". Is it better having 2 tasks (one for x and another for y) or set 1 task to find x and y.
4) I want the task running every 1 second from 10am to 11am every day. I set up scheduler and then cyclic but each one is independent.
Regards