1. In Ken Tidwell's rules translation it says that a worm can reverse direction "before it begins to move forward" if there's no room at all to do so. What if there's room to place just one or two segments? Would you have to move that many segments and then stop, or would/could you just skip your turn? Would it in any way break the game to always allow a player to reverse directions before each move?
Also, the same rule dictates that you can only reverse if "the segments of the worm remain touching each other" - what could cause them not to touch each other?
2. Is there a way to determine start-up locations except for drawing lots or something? As has been pointed out, being in the middle leaves you extremely vulnerable to being blocked, while someone at the edge has any amount of swerving space.
1. You must move in one direction during the turn. You cannot move two "spaces" forward and then backward. If allowed, this tactic would be usefull when you're blocked and need to move backwards, instead you could stay in place by moving one forward, moving one backward, moving one forward, moving one backward, ...
I think this means that you cannot break your worm at the beginning of the turn and join it back together later during the same turn. If it were allowed, it could be very usefull.
2. No, there's no way. Just start randomly. I (as the owner of the game) usually put myself in the middle, giving the other, new players a better chance.