Are satellites nowadays designed so that if one fails or its orbit degrades the scientists involved can send it various codes so that it will starts to 'beak-up' into smaller and smaller parts where when the parts are small enough they burn up in the atmosphere. So this automated 'forced breaking up' until its parts are small enough,could be a safety feature for satellites. Is this feasible?
No - satellites typically do not contain self-destruct devices. Malfunctions would be a) expensive and b) create lots of space junk.
What they do when a satellite is expected to enter is they will start it tumbling - the rotation helps the thing break up due to the re-entry forces hitting different parts.
If the satellite is defunct or has no maneuvering fuel remaining, it just burns up as-is hopefully not hitting anything important.