How to use 'sometime', 'some time' and 'sometimes' correctly

Students of English often get confused when it comes to the use of these three words, namely sometime, some time and sometimes. Hence in this post I shall explain how to use them correctly.
1 'sometime' means 'at an unstated time in the past or future'
e.g. I will go to your house sometime this week.
2 'some time' means 'a period of time'
e.g. My father spent some time explaining to me use to use this new machine.
3 'sometimes' means 'now and then or occasionally'
e.g. They sometimes go to the cinema together.