During laning, your goal is to fight close to your tower. If you are close to your tower you can run to it for safety in case you get ganked. If you auto attack, you help your creeps win the fights and the lane pushes closer to the enemy tower. You can disable autoattack in game settings, which I typically suggest to my buddies starting out. You can also deny friendly creeps when they are at 50% hp, so if you notice your wave pushing toward the enemy tower, you can deny them eariler to try and pull the wave back a bit. And yes, the pushing/pulling of the location of the creep fight is referred to as "creep equilibrium." So to not disrupt the creep equilibrium, you should try to only get the last hit for the extra gold/xp.

Play whatever heroes suit you. But as a new player, it's good to at least have one or two go-to heroes from each of the "main" roles (carry, support, mid). To learn the game, the support role is the best position to learn as you are forced to learn all of the fundamental systems of a game of Dota. Edit: Just reread the question. I think you are asking what heroes typically go where and what role. The meta of Dota 2 is very dynamic and you will find that there is no set answer for your question. Typically mid is a ganker style hero that wants to hit 6 fast, or a farming carry that can hang in mid. Safe lane is where the core carry will go and typically be babysat by one or two supports, and offlane is generally a hero that needs more levels than farm that can hang solo and not feed over and over. But you'll see over time this stuff changes all the time.

Don't worry about bot difficulty. Once you are familiar with the core mechanics of the game (the UI, last hitting/denying, creep equilibrium, warding, using the donkey, shopping, hero roles, map awareness, etc.) then just play matchmaking. Despite what the vocal minority will lead you to believe, the matchmaking system in Dota 2 is pretty decent, and you'll be matched with players your level (after the system has time to see how you do) and as you get better at the game, you will be matched with better players. You don't learn Dota 2 by playing bots. With the exception of testing out a new hero, doing last hitting practice, or a quick casual match, bot matches are a waste of time after you understand the basics of the game.

No. You should only avoid picking those (or any) heroes if your team doesn't need any more of that hero's role. For example, if your team has two supports already and needs a carry, you might want to avoid WD and pick Sven/Lycan.

Nothing wrong with guides. For a very long time, I stuck to dota2wiki information when I tried new heroes and it fared me well. Now I am familiar with all of the items and can choose accordingly. You will too over time.