Is it better to do a associate degree before bachelors degree ?

No. IF you did poorly in high school & need a second chance to prove you can actually perform at university levels, you must go to community college. Or if you must live at home, work, and go to school, then CC is probably your only option to keep costs down. Or if you want a vocational/occupational training program of 2 years or less, CC is absolutely the best way to go for you!

But if you aim for grad school, especially professional graduate schools such as medicine, dentistry, pharmacy, etc, then CC is a bad idea as you will have to retake your science & math/calculus courses to meet the much higher standards of university premed (pre-dental, etc.) programs. For some people, "cheaper" CC is actually a waste of time & money. Get into a highly rated 4-yr university to begin with, or expect a long-hard-haul and a lot of additional expense to have much chance, if any, of proceeding on your chosen path.

Its neither harmful nor helpful.  

A community college only offers the first 2 years of a 4 year ("bachelor's") degree and is called an Associate degree. Or, some Associates provide enough education in 2 years to enable you to get a "regular" job (often in the trades) [or, an A.A. in (say) bookkeeping, then go to work.] If you want some advanced knowledge ( i e be an accountant) you transfer in to a 4 year college or university and do the junior and senior level classes.   Many people start at CC because it is cheaper and the intro classes are smaller. However, people who start at a 4 yr college go all 4 years there, but do not earn / be awarded / an Associates degree.  That is the ladder of progression (then comes Master's, and PhD).

Not really. One possible advantage may be that an associate degree provides a recognised (lower) qualification for those who don't have the confidence to go for a bachelors or who are not successful a bachelors level. It is worth checking whether the associate degree gives exemption from an equivalent period on the bachelors. If it doesn't, it is likely to appeal only to those who do not expect immediate success at bachelors level.

Not necessarily. An associates degree is NOT required to earn a bachelor's degree.For many people, it is better to get an associate's degree because that should give you the knowledge and job skills to get a job. Getting a anchors degree may.not be necessary. 

It is better to get all of your lower division [Freshman and Sophomore] coursework for your proposed major done at a CC. However, once you earn a Bachelors degree, an Associates degree is a meaningless credential.