Hi ealxsweat, welcome to Bluelight

No this is not the wrong forum, although you probably could have easily found your answers by using the search function.
The effects of codeine and how long they last: Codeine is primarily an analgesic (pain reliever), anxiolytic (relieves anxiety) and sedative (makes you sleepy). It can cause some euphoria in some people. The "high" is mostly from feeling calm, relaxed and happy. Codeine also causes constipation, lowers blood pressure and heart rate, depresses breathing, and relieves coughing. Note that if you take it too often you can get physically dependent on it, which means when you quit you get unpleasant withdrawal symptoms. And also note that it is possible to overdose on codeine and the amount that would cause an overdose aries greatly from person to person. It should not be mixed with other CNS depressants like alcohol or benzodiazepines.
The main effects usually last from 3 to 8 hrs, depending on the person, slowly tapering off after that. It takes around 30 min to take effect.
Is it called 'nodding' when your on it: "Nodding" is when someone is on an opioid (codeine is one type of opioid) and the person is falling in and out of consciousness while in a sitting or standing position so their head nods. It doesn't always happen when on opioids.
How bad an allergic reaction to it could be: Side effects can range from feeling sick, weird, nauseous or itchy (all common side effects) to a full-blown allergic reaction. A full-blown allergic reaction can be serious and require medical attention, but is rare. After taking the codeine, an allergic reaction will be quick and usually start with swelling, hives, or sweating. It can cause difficulty breathing, dizziness, heart palpitations, shock, or cardiac arrest (if you have any of those symptoms seek medical attention immediately). More people have a sensitivity to codeine, which is not a true allergy, but can be unpleasant nonetheless. A sensitivity may cause headaches, visual disturbances, disorientation, flushing, tremors, agitation, blurred vision, disorientation, depression or convulsions.
Would i be okay taking 4, 30mg(codeine)/500mg(paracetamol pills, without doing a cold water extraction? Yes, if you're just doing it once 2000mg of APAP (paracetamol) should be fine for most people (unless you have a sensitivity to APAP). You don't want to go over 3000mg in 24hrs.
if i took LSD at 9pm would i be ok to go to college the next day at 11am? I would not take LSD for the first time when you have anything to do the next morning. It varies from person to person, but for myself, I would certainly NOT want to go to school or work the next day, and taking it at 9pm is kind of late and you will probably get no sleep.
Other notes: I would not take 120mg of codeine your very first time. You do not know yet how you are going to react to it. I would start with one 30mg pill. Some people get nothing from codeine (other than maybe unwanted side effects), some get average effects, whereas some people get very strong effects.