yes print it vertical - no support needed. You should have received an .ini file for Cura with th ecorrect settings. Even if you use a different printer the settings are a good point to start.
Indeed, print it straight up, I had to print one for a customer and was confused about it too, but it worked pretty well.
The only downside to vertically printing them is the fact that the layer orientation doesn’t help stability. Tell your customer to remove / apply the case with care.
indeed vertical. As a final tip I would rotate 45 degrees on the printing bed plane so you have a 45 degrees angle relative to your fans. This will make sure the fan blows nicely past the edges, dramatically improving the results on my Ultimaker 2
