How long should a CV for Masters application be?
Ok. The proper CV is the one that is well-tuned to a particular job. So, in general, there is no best CV template. If you apply for internship and other industry jobs, you might need a differenrt CV than when you apply for a master or Phd. 
The rule of thumb is to show the person who is reading your CV that you have the majority of the job requirements in their job posting. If it is a master program, then they probably have listed some requirement. You should try to tailor your CV as much as possible so it can show the best version of you in terms of those job requirements. For example, if one of one the requirements is having experience in doing research, then putting a research project you have done or a publication (if you have any) would help a lot. 

So, again, you should read the job requirement (in this case the master program requirement) very carefully and tailor your CV accordingly.