A and B are lies, C and D are deceptions. Your english is very good so I assume you know what a deception is though it might be a less common english word than, "lie".
I'm not sure if I can answer to your satisfaction without explaining some Christian theology. With morality, it seems that what Christ was teaching us is that it's more to do with the motives of the heart than the technical breaking of a law, and that this was the deeper meaning of the law.
To show what I mean, Jesus said to the pharisees that even though they technically did not break Mosaic law by paying the tithe, they themselves didn't have the love of God. (He knew their motive was just to look clean and righteous and perfect even though inwardly they were not good people, which was a bad motive.)
Jesus Himself when asked the greatest commandment answered;
Matthew 22; Jesus said unto him, Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind. This is the first and great commandment. And the second is like unto it, Thou shalt love thy neighbour as thyself. On these two commandments hang all the law and the prophets
So basically Jesus was saying if we were to put it into our own words, "all of you law-guys who think you are righteous and perfect and are happy to accuse other people, aren't as clean before God as you think just because you think you keep the law and understand it."
A: Motive - to have someone else blamed for something you did - A false witness and a sinful motive.
B: Motive - to escape punishment for doing something he knows would displease mom. He shouldn't have lied to his mum it is a lie but there isn't anything wrong in wanting to have fun as a child rather than working all day at school then having to do school again at home. So preferring to play games isn't a sin, lying to his mum isn't a major sin in this instance in that the motive isn't wicked like with A.
C: Motive - a deception rather than a lie, to basically not get told off for having fun. This type of deception I personally think is okay, he is using ingenuity to cover up the fact he had fun, using ingenuity to not be told off for having fun it seems to me neither are sins, it is not sin to play a game it is not sin to cover up the evidence of fun necessarily. I think the motive is basically not containing any wickedness in the heart.
D: Motive- to escape being told off however this time the motive of having someone else be punished in your place is again a bad motive as with A.
A is a lie and the motive of the heart is immoral. D is a deception and the motive of the heart is immoral. B is a lie but the motive of the heart isn't immoral, C is a deception but the motive of the heart is not immoral.
I propose this AXIOM;
In a system where any immorality enters the system, avoidance of technical immorality is impossible but this doesn't mean where such technical failures exist there is an immoral motive.
For example, in WW2 if I had been in that war and lived in Germany I confess I would have hidden Jews from the nazis, if the nazis came knocking on the door, it is okay to tell the technical lie that there are no jews in my house. However, if earth itself was free of all immorality, a technical lie could never have a benevolent motive.
Think about it - in heaven would I need to hide Jews to begin with? No, the circumstance would never arise. Therefore the technical lie of saying they are not in my house, only arises because there is already an immorality in the system, and that immorality is that people have chosen to murder Jewish people. In heaven there is no such motives, so there could never be a reason to technically lie.
For example if I was in heaven playing snooker
when God wanted me to be doing something else. If I was in heaven and I wanted something somebody else owned I might pretend I did not steal it. If I was in heaven and someone insulted me and God found out and got angry, I wouldn't tell God it was them.
Notice the crossed out events, no such events would ever happen in heaven. So then the only reason an immoral thing can turn into a moral thing is if the system is firstly contaminated by some form of immorality.
CONCLUSION: Our biggest mistake is to assume that the commands God is giving us come from an earthly source. They come from a heavenly place where there are no moral dilemmas.
This is my opinion on the matter. I am not saying I am 100% correct, this is just my take on it. I don't value my own opinion on this, greatly, which is one reason I don't like to give these type of opinions and reasonings because I myself am not that confident that I am correct about each instance (a,b,c,d) sometimes morality and doing what is right, can be confusing in a complicated, polluted system. I may well be correct to some degree, but I'm not sure - I think it's a much better idea to read what Jesus said, not what I say but I hope my answer at least makes sense.