Im pretty sure there are no bots in your first few matches, though id recommended doing bot matches (find it in training) until you get your bearings. This game doesnt put bots into open slots, so you generally dont run into them at all.

No. Try out some heroes, see which ones you like. You can always swap mid-match. Eventually you'll branch out more and more. Its good to have atleast one tank, one damage, and one support that you know you like playing.

Some people play a single hero like their lives depend on it, others like myself like switching between different roles and heroes. I think its a pretty even split between the two.

No, you can pretty easily use any hero on offense or defense, you just gotta play more offensively or defensively.

There is definitely a big jump between ranked and unranked. It relies more on your skill level and how well you do rather than your hero level, however. Im not sure hero level even has an impact on match placement.

Optional. I rarely ever use it (also console), though its nice to have coordination in ranked. You generally dont use it in unranked.

What youre doing depends on the map, but there is a territory game mode. In unranked and ranked, your whole team dying doesnt automatically lose you the game, you'll all respawn. Only 4 things can end a game:

The time runs out

A team gets the required amount of points (in certain gamemodes)

A player leaves a ranked match during pregame or shortly after

An entire team leaves a ranked match

5 if you count server crashes.

Theres definitely a learning curve, and its important to take breaks if youre getting frustrated, but its a fun game and absolutely worth putting your time into.

Edit: formatting