Silver Surfer for the NES is way harder than TMNT. It’s possible, though I’ve never done it, to beat TMNT. AFAIK , Silver Surfer is actually possible to beat, but basically no one has done it.
I wouldn’t call Roblox itself a gacha game. That category is the ones where you are trying to collect all the heroes in the game and level them up with rare loot. AFAIK they generally, if not always, involve loot crates that you have to purchase.
Roblox has its own problems. As spelled out by People Make Games in these two videos.
Roblox claims to teach kids how to make their own games. At this point from what I’ve heard, I would suggest Unity Engine before Roblox, and I wouldn’t recommend Unity after their pricing debacle.
Watch the videos, and have a serious discussion with his parents about it before you get him that game platform.
My family would play this as a group. We napped at least the first 12 levels, maybe more. My father loved making maps of old video games. I’m certain that his map of the thieve’s cave in Adventure is still floating around the house somewhere.
You’d probably be able to 100% Turnip Boy Commits Tax Evasion. Only about an hour or two to finish the game, and another 15-30 minutes to figure out the two extra achievements.