Of course you can get the final upgrade! First, you gotta buy everything else. You have to fill up the alphabet completely, and then get the "ALPHABET! ALPHABET ALPHABET!" which will make trollface fall through the floor and end the round. Then on your NEXT launch, you have to get the letters to spell out TROLLFACE, and you'll be able to buy it. For a dollar.
Problem?
Here's an issue...I've clicked on every single thing in the skill tree, there's nothing left to get. I have 10 points for INT that can't be spent because everything is maxed out, and yet to max out the other categories I would need 30 points of AGI, 40 points of DEX and 30 points of CHA that simply don't exist. the numbers just don't add up. Fun game otherwise.
To anybody having an issue with the badge registering, it isn't broken, it just takes a few minutes for each level to communicate with kong. I walked away for 15 minutes and when I came back the badge was registered.
For those trying to get the quest badge: If you're having a horrid time trying to do it on the 1st "easiest" song, try this instead: I did it on "My heart up your ass" which is classified as "tough" but is also only 58 seconds long and not really that hard. Also make SURE you hold the sustains all the way, or you can hit every note and miss the "perfect"
 "Undress the sexy bride"){kind=icon}
 "Trollface Launch"){kind=icon}
 "Elephant Quest"){kind=icon}
 "Two Rooms"){kind=icon}
 "Zombie Minesweeper"){kind=icon}
 "Grid16"){kind=icon}
 "Crush The Castle 2 PP"){kind=icon}
 "Super Crazy Guitar Maniac Deluxe 2"){kind=icon}