You came to the right place here in the forums, to meet the great CM community in here... you can learn a lot of information about your faith, singles issues, and current events... or just stop by and have some fun in the various word game threads and trivia threads.
As for your questions: First, you'll find out you've been blocked by someone if you attempt to send him a message or emotigram, and instead of it going through you get a message from the site telling you that so-and-so has closed communication with you. Also, I'm not sure if this still applies, but for awhile if you tried sending three consecutive messages, and the other person never responded, the site would block you from further correspondence until the other one responds.
If you send an emotigram, and only get back a "thank you" but without any words, chances are they are a non-paying member, and this is all they can do without paying up (which you never know, they might just do if they find you interesting and want to correspond). Be sure to put some words in your emotigram, and not just a wordless "hello", so they know you are a paid subscriber.
Have fun on here, Carolina, and welcome to the Forums!