Only can be an adverb or an adjective. Furthermore, as an adverb it can modify a verb or an adjective.
I only went there to see Becky.
I took the only piece of candy left.
There was only candy left.
Because of this, the position where only appears is crucial - the speaker/listener will associate it with the closest word.
So all of your sentences mean different things:
I only sell apps to the young person.
You don't do any other action besides selling apps to the young person.
I sell only apps to the young person.
You don't sell anything else but apps to the young person.
I sell apps only to the young person.
You don't sell apps to anyone except the young person.
I sell apps to the young person only.
You only sell apps to one person, and that person is the young person. This isn't too far off from the previous meaning.
Furthermore:
Only I sell apps to the young person
No one else but you sells apps to the young person
I sell apps to the only young person
There is only one young person and you sell apps to him.
First off, we must remember that "though" can be used as a conjunction and adverb, whereas "although" is a conjunction; it's never an adverb. So "although" and "though" are only interchangeable when they are used as a conjunction.
As a conjunction, "though" is much more common than "although" in speaking.
When used as a conjunction, "though" or "although" can be used at the start of a subordinating clause whether this clause comes before or after a main clause.
As for the "though" as an adverb meaning however, you usually use it at the end of a sentence.
In the sentence "It was a good game though" presented by the OP, the "though" has been used as an adverb.
Best Answer
"Behave" is a word that, without any modification ("behave badly", "behave strangely", "behave well"), automatically carries the sense of "behave well".
More, without modification, it also carries the sense "behave oneself", so to quote the Cole Porter song (from his 1948 musical 'Kiss Me Kate'):
"Why can't you behave?
Oh, why can't you behave?
After all the things you told me
And the promises that you gave
Oh, why can't you behave?"
By the way, the second verse says much the same thing with different words: "Why can't you be good?"
... "Why can't you behave?" means 'why can't you act in the way that people expect of you (that society expects of you)?
... "Why can't you be good?" means 'why can't you conform with society's expectations/the law/your religious precepts (and allow your actions to be guided by these)?'
'Be good, 'be bad' have to do with one's character, whatever makes one act in a good or bad way; 'behave', 'behave well', 'behave badly', 'behave yourself' are talking about the actions themselves and any assessment of character would be by inference. But because one's actions are so closely determined by one's motivations, "Why can't you behave?" and "Why can't you be good?" mean virtually the same thing!