The Defenders in Marvel Comics have a changing lineup over time. Some of the notable members are Jessica Jones, and sometimes even characters like Hulk or Valkyrie join the team depending on the storyline.
The number of Marvel comic heroes is constantly changing and growing. As of now, there are well over 8000 characters, but new ones are always being introduced.
It's not a straightforward yes or no. Some comic shops might offer discounts to attract customers at SDCC, but others might keep their prices the same. You'd have to check around to find the best deals.
Marvel's Defenders has a mix. It keeps some core elements from the comics but also makes adjustments to make it more engaging for the screen. Some fans think it's close enough, while others notice the deviations.