That depends on what resource or material your using it all depends on that. But most people that get 99 skills it takes them years.
If you buy monthly - 30 days, 3 months - 90 days etc.
100
The sale is over.
It depends on how many hours a day you'll play RuneScape.
5
About 500 if you add all the colors together. They have gotten quite rare these days.
I would say the best skill has to be Magic, mainly because it has so many uses, you can use it to smith ores, trurn items into cash, fill water vials, freeze opponents in battle, get around runescape, and mainly use it to fight, heal cure and teleport other people and yourself as well.
That Entirely depends on how many hours a day you play runescape.
The answer would probably be impossible to find out, sorry.
there are 23 skills in runescape
What town? There are many towns in Runescape.
It depends on what one you get if it's one month it will usually add 30 days, if its two months then 60 days and so on, so its 30 days per month.