Yes you can pinch them back now, in fact they should be pinched now to make them more compact. You take pruners or scissors or finger nail and pinch where there is a leaf break or the center. If they are real leggy you need to pinch them back pretty hard. Being raised from seed doesn’t make any difference, when you buy them in a garden center they are from seed. I normally pinch the old blooms off before I plant them in the ground. Thanks for the question .

No you always cut just above where a leaf is on the stem. That is where the new break will be. You only cut the plant the height you want. If you want to cut about an inch off the plant, go to where a leaf is and cut just above where the leaf is on the stem. You can make the plant as high and as low as you want it to be