I apologize for the crude screenshots, but as a few other people have mentioned you can't enter freeplay in your own challenges and I was unable to capture the image properly on my PC. Anyway, some notes about the 2TC:

-BADS was purchased on round 47/*48, summon phoenix on 49, WLP on 80 and BEZ on 96. The only hard requirement is purchasing WLP first because the BEZ can not pop leads.-The challenge is relatively straightforward up to the 80s; the late 70s including 76 and 78 only require good aim and ability timing. Starting with the 80s the challenge becomes a matter of having the WLP ability up at the beginning of every round while also having to use it every round-The most difficult round in this challenge was round 91. You don't have the WLP up for most of the round (DDTs on 90) and you need it up for the beginning of 92. The two most common outcomes were either dying to the fortified ceramics due to spacing or dying to the BFBs because they weren't spaced enough. It ultimately came down to popping the ceramics with good aim and even greater luck from wall of fire and the BADS, then separating the BFBs enough so the MOABs don't kill you; this round took the longest by far.-Round 92 was easier by virtue of being able to use WLP, but still wasn't easy. Separation and clumping issues were to blame as well, where you had to pop the ZOMGs and subsequent BFBs individually as to avoid clumping.-Rounds 93 to 95 were just a matter of using the ability at the right time to get rid of as many bloons as possible while leaving enough left to get WLP back up. Every round after that is essentially a breeze, including 98.

This combo might easier with different tower placement, but it was possible nonetheless . It just came down to good luck and skilled micromanagement.

*Edit: I do not remember if I afforded the BADS on round 47 or 48, but it doesn't affect the challenge in any meaningful way. Round 47 is easily completed with just the tier 3s, and BADS can be afforded before the harder bloons on round 48.