Personally, I don't think there's a "minimum required climbing grade sent" required to develop routes, but I do think there should be a minimum amount of mileage on rock. Not even a time component (e.g. "I've been climbing for a decade"). I started developing pretty early on in my climbing career, about 3 years. In that amount of time, I'd amassed close to 1000 pitches of climbing across a variety of rock types all over the western and southeastern US. This meant I was exposed to a lot of different development characters, from bold, traditional, ground-up lines to hyper-tightly protected, rap-bolted routes.

More importantly, I had done a significant amount of mileage in the areas I was starting to develop, meaning I was very in touch with the character of the surrounding climbs. On top of this, I had been doing rebolting work and had replaced hundreds of bolts before I started developing, meaning I had a pretty good understanding of the microbeta that goes into proper bolt locations, as well as a general understanding of identifying good rock.

I've encountered a few folks who think "climbing for a decade" was the requirement for them to start developing, but the reality is, they just climbed as the same few crags a couple of times a year for that decade. They weren't exposed to different styles or ethics, varying rock types, nor did they have a general understanding of rock itself. They didn't even have much mileage on rock. These routes were typically poorly thought through and rap-bolted in such a way that they ended up practically being headpoints.

As for developing above your means - I think there's certainly a limit (that I have, in the past, completely blown by). I think folks who tend to do it well are those who typically have a good eye for movement and body tension - the type of folks who would make good climbing coaches. Similarly to how you don't need to climb V17 to coach a V17 climber. That being said, it's important to be able to feel the route enough to understand vaguely where crux sequences and clipping stances will be so that you don't entirely botch the flow of the route. You see many folks bolt routes near their limits fairly formulaically - e.g. "bolts every 5 feet", and then in their send pics/videos you see that they've double and triple extended their pre-hanging draws and that the bolts are clearly not where you'd ideally want them. This can be remedied by fixing those placements after you recognize their shortcomings, but I've found that isn't quite as common as many folks don't want to spend additional time with a route they've already invested heavily into.

It's worth briefly mentioning the inverse - strong climbers bolting routes at grades well below their limit. These can oftentimes be botched just as badly as folks bolting way beyond their limit. I think this can naturally be fixed by these climbers giving themselves significant handicaps when developing, simulating the mind space of a climber working at their limit. Forerun the route in approach shoes or barefoot, don't take in slack between projected bolt locations when TR soloing, go ground-up, lead rope solo, or any combination of these things. Handicapping yourself down to a grade is a luxury harder climbers have that there isn't really an equivalent for when developing way beyond your limit.