Earning through doing class assignments and exams for people

Q: I have a question regarding one domain of modern day freelance work. People contact me through the freelancing website (where I have my profile made that mentions the subjects that I'm expert in) and ask me to do their class assignments and projects. Sometimes, they also require help on their tests and exams both online and inside the class. We decide a price with mutual consent and I get paid once the work is delivered.

Now I have a couple of questions:

1- Is this mode of earning permissible?

2- If not, then what about all the money that I have earned and spent on myself and my family till this time and this amount will turn out to be not so little as I've been working in this mode for last 2 years.

3- What about the profits and investments in the property and other traditional businesses that I have done using this money that I have earned from the above mentioned work mode?

4- What about the savings that I have in hand for the time being?

Doubting whether wetness is mani or discharge when waking up

Q: I got up and noticed wetness but as I was having this kind of discharge most of the time nowadays and before sleeping there was some discharge, so I didn't do fard ghusl and read fajr and recite Quran. But I was feeling like I was sinning as the amount of discharge was not this much before sleeping and on the other hand it was like normal discharge which I was experiencing normally. Now is my salah valid or not?

Semen retention

Q: Is semen retention (meaning after going to wife and not releasing semen) permissible? This is a meditative art to control the mind and body. I want to ask you that if I do not release semen or sperm after intercourse for 4 to 8 days? I don't do this for birth control but just for maintaining energy in my body. Is it permissible to do so?

Celebrating the birthday of Nabi (sallallahu alaihi wasallam)

Q:

1. According to the hadith, immitation of kuffar is haram. So if I eat a birthday chocolate someone gave me and went away, is it harasm? Because its a non-Muslim practice to celebrate birthdays.

E.g. If I got a chocolate on someone's birthday and I kept it and after 2 days I ate it, is it haraam because that chocolate was purchased for a haraam act which is celebrating a birthday which itself is immitation of kuffar?

2. Ruling regarding celebrating Nabi Muhammad's (sallallahu alaihi wasallam) birthday. Is it imitation of Christians, because they celebrate Christmas like Isa (alaihis salaam) birthday?

3. If a Quran is printed in an industry, like from softcopy to hardcopy, then is it man made or Allah made it? I mean if everything Allah created then what about the above case where hard copy of Quran was made by using a machine. Is it then machine made? Also if a man writes whole Qur'an, just as one photocopies, was the Quran made by a human because a human was the one who took ink and paper and wrote the Quran and compiled it or Allah made it?