The first thing to note is that eMC does not have an anti-spam feature and relies on the email provider server to carry out an anti-spam function and then reacts to this.
I know that some users attempt to create rules to solve the issue of Spam (I only use Rules to move messages to specific folders) personally I do not do this and use an antispam program, a search will show a few programs some of which specifically mention eMC.
I can not help you with your questions #1 & #2 other than to suggest you use F1 to launch eMC Help when the program is open.
Question #3 No eMC does not have RegEx capability, the program I use does if you know how to compile RegEx strings.
Maybe someone else can give you specific help with Rules.