(First, I only played through the first three screens; this is some quick feedback based on those.)
I love super hard games! The only thing is… the best thing about IWBTG is the variety in the levels and how utterly, destabilisingly vindictive they could be. A lot of the fun wasn't just planning your way around a visibly difficult level—it was the surprise when the level revealed a whole new way to be hostile to the player. Spikes randomly falling down (or up) on you, randomly deadly scenery, invisible blocks… It kept you on your toes, and made every new screen a (masochistic) joy to explore.
By contrast, I played through a few screens of IWBTMango and very little really surprised me. Being flipped upside down was a global change; IWBTG excelled at defeating your expectations to the point you came to expect shenanigans on every single screen. Here, my biggest surprise was that everything was exactly what it appeared to be. I suspect this is going to change as you continue to work on it!
Another thing about IWBTG: it had just enough "tightness" to play predictably. The controls felt reasonably precise (though not great) and the hitboxes were modest, so you had a good idea of what was possible and how to go from intent to execution in advance. With this, there was something slightly… slippery. The controls never quite felt natural (especially reaching up to press R when I wanted to restart), and maybe I'm slower than I used to be, but the hitbox on those bugs in particular seemed a bit generous. I know both of these are extremely tough to get right! Just wanted to mention them as they're very fundamental and you're looking for early feedback on what looks like a promising tribute!