1. Fernco type coupling, possibly for expansion and contraction, but pipe should have been wrapped or isolated, so as not to come in contact with cement (different expansion and contraction rates). Misision CP (castiron to plastic) 33 is the listed choice for transitions between different material CK = ( COPPER TO PLASTIC, STEEL OR CAST). As long as the listing approves the use (or it is required) you can leave the coupling.
2. non sheilded couplings typically are not allowed inside of structures this includes below ground, I have found in the listings of the manufacturerer some that are approved.
3. the ginormous plate is now required (both top and bottom) if your municipality has adopted the I.P.C. codes