Well done for making a playable Game Boy game, all of this feedback is based on me playing it on a Game Boy DMG. I really enjoyed the start, it seemed like I was going to enjoy it, but after I collected the D-pad and entered the large open space, most of my time was spent looking for something. I gave up after I collected the A button. To get to that place seemed so random, it took me forever to find that small black mark on the right of the map. Before that, I collected the thing on the pedestal, but it did nothing except make the game slow down. There was no music unfortunately, so it was a frustrating and silent experience that I couldn't finish. Once I collected the A button, I tried the gate and the boat but nothing happened so I'm sorry I couldn't finish it. I hope this is some useful feedback and will help you in some way.
However, I love the idea of collecting parts for your Game Boy and I liked the game up until I felt lost in the large open area.