Various questions [Ender3v2]

Hello, I have a few questions regarding printing on Creality Ender 3 v2

1) At the start of the print the printer prints a straight line across one side of the bed - is this normal? Or some issue with levelling? (I don't mean the line that it prints around to-be-printed model)

2) Is there some was to influence the quality of the print? I printed the sample dog figure (some scuffing) and then my model - a cylinder with an extruded ring in the middle (but top side of that extrusion was not closed off / printed over, you could see the internal structure that printer does when filling in a continuous space - ATTACHMENT)

3) My last attempt with another cylinder ended up with the cylinder tipping over during the print - do you have any tip to prevent this? Right now I modified the model to add it a certain base which I then will try to file off, but what if this is not desired?
I was thinking of using something to fix the already printed part in place, but I worry I will move the model even if slightly.

Thank you

1) The straight line up the side is a purge. This is just to get the extruded primed and remove any dangling filament. I believe this is added by default in your slicer, Cura has it in the default pre-print g-code.
2) That shape is difficult to print without supports. Are we looking at the bottom of it?
3) The shape is too tall on too small a base, enable a brim to print a wider, thin area of plastic around the base to hold it down. The brim will have to be torn off (or cut). Also, enabling the supports as per (2) will help to stabilize the print.