Ok... sounds like you're new to growing.
Get an autoflower and stick it in Loblaw supersoil.
1. The size of the plant depends for the most part on the size of the pot. So use something a little bigger than a solo cup. But not much bigger.
2. If you want a single cola, cut off side branches.
3. Don't cut the side branches. Tie them down. Read a bit on LST (low stress training)
Now that it's legal, why do you want a plant you and your buddies will smoke in one long weekend?
If you want to grow one on a balcony, start topping it when its small and train it to go wide.
It'll take you at least 4 months to grow and cure a plant. Max that time out and make it worth it. But be warned, if you plan on letting the plant go with out watering 2-3 times a day ,on a hot day, it'll die.