What is the minimum number of lines to separate the sets?

Observe the graph below, it is possible to separate linearly with a line at least two of the classes?

How many circles are needed to group all points into three groups with 2 points and a group with 4 points?

I believe the answers are

1. 3
2. is not possible
3. there will always be points left over

These challenges were proposed to me by a discreet math teacher and, as they are "challenges", I don't imagine that the answers are so simple.

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