Mi venis por doni la saman demandon. Havu lingoton.

sonĝi—to dream while sleeping.
revi—to dream about an imagined future.

So, Martin Luther King, Jr.'s "I have a dream" speech is called "Revon havas mi" in Esperanto, not "Sonĝon havas mi".

Not exactly. The -ec- affix means something like "the concept of" or "the quality of" or "the state of".

Belo and beleco can both be translated into English as "beauty" but belo is like a beautiful thing or the abstract idea of beauty, and beleco is like beautifulness, the quality of beauty.

There is some useful explanations of -ec- here: https://adventuresinesperanto.wordpress.com/tag/affixec/