That sounds like a pretty tough one to diag without looking at the car but I can certainly help you eliminate stuff with some easy checks.
First of all, if you feel like your dad or yourself are mechanically inclined I have a few checks you can do to start eliminating things to help to start to narrow down issues.
If there is a noise you have to figure out if its engine noise or drivetrain noise. That can be really tough for an untrained ear but sometimes engine issues can cause drivetrain noise so the stuff im going to tell you to do will be good for your car no matter what. Its pretty much a process for a "true" tune up that will make very big leaps in driveability of car.
First, the codes you mention all go hand in hand. Knock sensors are small crystals that produce AC voltage when they are vibrated, which means your crankshaft of your car vibrated enough from most likely a ignition issue called detenation ( the spark plug fired before top dead center of the pistons compression stroke causing the crankshaft to shake violently sending an AC signal to the ECU which will automatically set off a CEL). This is a very big issue can destroy an engine in a hurry, but modern electric fuel injection systems will lean out the fuel mixture of a car till the knock sensor starts to vibrate and sends a signal to the ecu to stop advancing the engine timing. The reason the engine wants to run so lean all the time is to get emissions as clean as possible. Most knock sensor related DTC's are from ignition issues or unmetered air getting into the cylinders ( faulty spark plug, coil packs, intake leaks after the throttle plates ). I would first of all, suggest checking your spark plugs and their gaps. Spark plugs from factory will have incorrect gap 80 percent of the time from shipping and being thrown into giant piles after production, so pull your plugs and check gap. If your car is a coilpack ignition system, its a little tough to check coilpack function unless you know exactly which cylinder is acting up and you can swap the coilpacks around and see if the problem follows the coil pack from cylinder to cylinder. If you have a waste spark/distributor system, you can check resistence of your spark plug wires with a multimeter, the specs can vary car to car but a standard spec to follow with high tension spark plug wires is 7 thousand ohms per foot of cable with a total maximum of 30 thousand ohms allowed total per wire. Very easy to check the wire if your car uses wires, just unhook take your meter and put one lead on each end of the disconnected wire and switch meter to ohms. Repeat that for each wire. You can also check availible voltage to the spark plugs with a spark tester, but im not sure if you are familiar with that tool.
Another possible issue is with air supply. Find out if your car uses a MAP or MAF sensor to meter air going into the engine. Some cars will use both sensors for a air measure system called speed density. If your car has a MAF it is very common for a dirty MAF sensor to cause exactly the problem you are describing. Remove the MAF housing and look into the backside and you should see a tiny wire strung across the housing in the center. Use pure alcohol and a q tip and be VERY careful ( im talking insanely careful, its super easy to break that wire) to LIGHTLY dab the wire and resistor with that alcohol soaked q tip. After you clean the maf, let it sit out in the air for a couple hours to completely dry out and reinstall. Even if this wasnt the issue, it will make your car run like new when the other issue is resolved, people often over look the cleaning of the MAF and can never get a car to run like new again. After cleaning of the MAF sensor, Inspect your throttle body and see if there is any carbon build up blocking the sweeping path of the plates. If there is some crud in there, clean with alcohol in the same fashion. DO NOT get alcohol into the intake of your engine without removing the throttle body , it can blow up your motor if youre not careful.
The cat fault from your ECU goes hand in hand with the knock sensor. The second there is any misfire on a car, the cat code will automatically come aswell. If you feel your cat is clogged, you can physically hear it when you rev your engine under load ( foot on brake and gas with park brake engaged all the same time ). The sound will be an odd sound from your intake system and smell from the intake.
There is no way you can check your o2 sensor without a proper scan tool. I would try all this other junk before you randomly go buy an o2 sensor, not to mention there is 2 o2 sensors on most cars. One before the cat, and one after. Their primary job is to monitor cat performance. There is no way to check an o2 without a lab scope.
This is atleast a start, if you have any questions, let me know dude.
