Need Clarification on Low Compression, Rod Bearings, and Engine Knock?

Yes all the things you meantioned would destroy an engine so ..Just to clarify every part inside the engine works together to form a complete engine eas one having an equally important role and since they all work together to insure the longevity of the engine its essential that every part inside it is in nearly perfect condition if evan one of the parts gets damaged in the slightest way the overall engine is effected in some way weakening the engine ..especially the the parts you meantiined .. when those parts go its catistofic damage and ends the life of the entire engine ..and these days its usually vary expensive to rebuild so the engine is usually just replaced either with a new factory engine from the dealership or a known good running used engine preferbly with low mls wich might be a bit cheaper that is usually whats used most and thats sort of the quick easy way to explain it without getting to technical that would be like a journey to Jupiter and back i wish you the vary best of luck hope this helps

Thank you, that explanation helps a lot.
Just one more clarification — if an engine has low compression in one cylinder and begins knocking immediately after installation, would that indicate internal damage that existed before the engine was installed? And can low compression contribute to bearing wear or engine seizure over time?
I have a few follow-up questions about my engine symptoms.
The engine gives off a sulfur/rotten-egg smell when going uphill, the oil level keeps dropping, and the knocking noise gets louder when the car is in Drive at a full stop.
Can you explain what these symptoms usually indicate?
Do they point to internal engine damage, misfires under load, or bearing wear?
And can low compression in one cylinder cause this combination of symptoms?

Its usually a result of simply not checking 2 fluides coolant and oil theyre the two most important components in the engine (and easiest to check ) that said"...Worn bearings are a big deal the engine is in really bad shape if theyre bad or worn usually gives up the ghost shortly after going bad ..and poor compression usually goes along with that but isually to late by then and many other things.. one of the big things is you loose your oil pressure wich is the life blood of the engine so it can die shortly after that but as I described earlier these parts all work together when anyone of them get weak worn out or breaks they all suffer like a chain reaction somtimes over time and somtimes vary quickly and in turn the entire engine fails and its really bad if anything breaks or wears out prematurely and like said its usually a result of human neglect be well hope this helps

And yes I'd say if the engine was knoingbright after it was insatalled you might have got a bad one that was neglected by the previous owner ...the good news is in some places there may be a 30 to 90 day warenty on used engines somtimes you can just go back and they might just give you another one if it hasn't been to long already ..you never know never hurts to contact the place where you got it ...good luck wish you the best .