Continuing the discussion from Welcome to our forums! Please introduce yourself 
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Answers are based on your use of SketchUp Free (web) which is what you indicate in your profile as the version you are using.
No. Not specifically, You can use the basic drawing tools to model a slot of whatever shape you want.
Connecting two arcs is probably the simplest way to do that.
No. You can choose the desired units in Model Info and even change them after you’ve started modeling. Depending on what it is you are modeling you might want to model at a larger scale. SketchUp is foremost an architectural modeling application. Although your can model small objects, it is sometimes useful to model them larger than real life. For example you might choose meters as the units and treat them as if they are millimeters or inches. For example, this is screw is M6 but I modeled it such that the major diameter of the threads is 6 meters.
You can set up the camera to show your model from the view you need. If you want to create a 3-view or similar you can make copies of the part and rotate them as appropriate. I did that for the views of the screw in the above illustration.
Here copies of the object rotated for 3rd angle projection.
And the result with one mode copy and a few dimensions added in.
Take some time to go through the instructional materials at learn.sketchup.com and the Square One videos on the SketchUp YouTube channel.