Sorry Lovey Dovey but its not "anything and all things related to the task." The SC can follow things which they find DIRECTLY from the investigation or from 28 cfr 600.4(a).
Again the Primary mandate is for Mueller to INVESTIGATE the Russian efforts to interfere in the 2016 election. Its not mandated to investigate a CRIME.
So Yes, if it finds a crime in its investigation it can pursue it and prosecute Federal crimes.
Which resulted in the conspiracy charges you mention.
But and its a BIG BUT, the conspiracy cited in the indictments you presented isn't along the lines of Mueller's mandate about investigating the Russian government's interference in the 2016 election. They are for other reasons.