"You cannot redeem Bonus Code on this Account"

Quemapueblos: Yes, if you sell your VK you can still buy or even research the tiger (if you have enough experience on the VK or free exp built up). Selling a tank does NOT affect your tank's experience earned or what can you research from that line. Often I get a little antsy before i get enough credits and sell the tank to buy the next. Be sure to have enough money for ammo and mounting modules for your new tank. I've had to grind a few battles in order to field my shiny new beauty a few times lol