What are the drafting and blocking rules on the bike?

Is drafting allowed? (World Triathlon rule 5.5 a) For age-group triathlon:

In draft-illegal races:

• The draft zone is 12 m long, measured from the leading edge of the front wheel of the rider ahead.
• You may enter someone's draft zone only to overtake, and you must be seen to be moving through it. You have a maximum of 25 seconds to pass through. Several failed attempts to overtake in a row can be called as drafting.
• You are passed once the other rider's front wheel is ahead of yours. You must then drop back out of their draft zone, continuously moving backwards. Re-passing before you have dropped out is a drafting violation, and so is staying in their zone longer than the time allowed.
• You may be in a draft zone for safety reasons; within 100 m before and after an aid station or transition; at an acute turn; or where the Technical Delegate has excluded a section of the course.
• You must refuse others' attempts to draft off you. A rider who moves up to take advantage of a draft is responsible for avoiding it.
• Drafting off a vehicle is also banned. Its draft zone is 35 m.

In draft-legal races, you still may not draft off a rider of a different gender, a rider on a different lap, or a motorbike or vehicle.