Hi, the game is designed for PAL but it's NTSC compatible.
About the cartridge compatibility you'd better contact BOBR Games here:
I really thought there was the list of the programs used to make Lester in the game description... but there isn't O_o
Anyway, Lester is made with...
Code: TRSE
https://lemonspawn.com/
Gfx: Charpad PRO and Spritepad PRO
https://subchristsoftware.itch.io/c64-pro-editions
Sound: GoatTracker
https://sourceforge.net/projects/goattracker2/
Regarding my experience this is my first game ever. Not for the C64 but for every platform. But I'm a good player and in all those years I developed a taste for a certain type of games and I tried to reproduce what I like about them. Or, at least, the things reproducible on an 8-bit machine.
What I like about the C64 is that despite its infinite library there are few games that explicitly try to mimic the japanese productions on consoles and home computers. The great majority feel so 64ish. But what I learned with much surprise in those last years is that it's more a design choice than an actual limitation of the machine. Despite the heavy limitations of its graphic modes the C64 has a palette that is more colorful and vibrant than what the average 80s game made us think. And Lester is not even the best demonstration of this because I choose to have a dominant color per section which made my life a lot easier but take a look at Sam's Journey. What they made is insane and a testament of the VIC-II real capabilities.
Regarding the next game I'd like to take again inspiration from productions on other machines like I did for Lester which was a love-letter to both MSX and NES platforming, but this time looking to the other side of Japan... late master system/early mega drive era.