Difference Between Data Science and Big Data is really complicated. Data Science is a field that comprises of everything that related to data cleaning, preparation, and analysis. Big Data refers to humongous volumes of data that cannot be processed effectively with the traditional applications that exist.
Is SHELL needed to be a Data Scientist? the answer is Yes, SHELL ( Shell is the sleeping beauty of Linux ) is Needed for Data Scientists to get the data and to work with that data. Everyone is busy to Learn R or Python for Data Science, learn Shell for Data Science.
SQL is needed to be a Data Scientist. We have to get the data from databases and to work with that data. Without Database Data Science is meaningless.
R vs Python, which one is better for Data Science, finding the best one is always a heavy task. Python and R both the languages have their own features.