Cura versions and 'priming' border

I've been playing with my new printer and have, for the most part, been getting 'ok' prints. Was using the PLA thay gave me with the kit, but have now switched to the PETG that I bought. Overall, the PETG is workign well - I think I need to figure out the start to get good adhesion from the start, but that's part of the reason for this post. PETG is 'drippy', I'm sure you all know what I mean, and the PLA really wasn't much less 'drippy'. The first thing I printed was 'iffy' in the bottom layers and basically failed in the top layers. I peeled away the top layers for one of the prints and under those layers, it was perfect. I was playing with Cura 15.04.6, which is what is required for settings if I want Octoprint to slice the models (Octoprint is quite nice, I must say), but when I went back and looked at the layers view of the knob that was failing at the top, the layers are all kinds of goofy in the layers that failed. I installed Cura 3.0 and 3.1 and loaded the same STL file and sliced it, and looking at the layers view, the layers that appear goofy in 15.04.6 appear to be perfect in 3.0 and 3.1.

That brings me to my first question. In 15.04.6, I don't know what the setting is. but models sliced by it print a 'priming border', for lack of a better term. It's I believe three passes outside the print area that I can only assume are intended for priming the nozzle and filling it to replace what was lost to 'drip'. I can't figure out what that setting might be and the newer versions don't do it by default, and I can't seem to find it. That seems to help with the printing as the 1cm cubes I've been printing to test since they don't take long have been doing well with them. The first side or so tends to get no extrusion, but after that, it lays a good bead down.

The second question is with dual extruders - in 15.04.6, I can tell it that the machine has dual extruders, and when setting up the print, I tell it '0' for the second hot end, and it's happy and prints - do the same thing with the newer v3 versions and it croaks. I assume looking for something with the second hot end. If I tell it the machine has only one extruder, it prints fine. How do I tell it 'ignore this extruder' so I can have it set up for dual extruders, but if I'm not using both, not have to change my machine/machine settings?