If "tycker" means "to consider" and "om" means "about" can this expression mean "You don't need to think about it"?
the construction tycker om means like as in I like that girl or I like this steak. As to why that is, you'll need to consult your fantasy and/or etymology dictionary.
Very well, I know this meaning of "att tycka om" construction but I met with expressions like "Vad tycker du om mig" translated as "What do you think about me" (it's translated this way by Google Translate) and I wonder if it's correct.
Yes, it has that meaning in combination with vad.
There are two different verbs: tycka om, the one we have in this sentence is a particle verb, where the stress is on the particle, and the other one is just the verb tycker 'thinks' plus the unstressed preposition om.
However the above sentence is not ambiguous, since if there is not question word, it will be interpreted as a particle, and just mean 'like'. Here are some example sentences, and none of them are ambiguous:
Vad tycker du? 'What do you think?
Vad tycker du om? What do you like?
Tycker du om det? Do you like it?
Vad tycker du om det? What do you think about it?
Vem tycker du om? Who do you like?
Vem tänker du på? Who are you thinking of?
Tycker du om honom? Do you like him?
Vad tycker du om honom? What do you think about him?
I don't understand how vad tycker du is so different with the added om. Is tycker alone think, and tycker om like? so it becomes a new verb?
Yup, the stressed om makes all the difference. It's a different verb. The same kind of difference as in turn vs turn off.
"Du behöver" translates into "You need" and "Du måste" translates into "You must"
How would you say, in Swedish, ''You need to not like it -- you need to dislike it.''?
Intuitively, I'd say that would be Du behöver tycka inte om det. Simply moving the negation to the appropriate verb.
Though my opinion is not that of a native speaker.
That would actually be an unnatural and wrong sentence it would be "Du behöver tycka det är dåligt"