As much as the motherboard/bios will allow, which is next to nothing. It doesn't matter what YOU want, it's what the bios allows. There are no switches to allow all core turbo, if there's no switch then there's nothing to turn on.
You might want to walk around the world. It might be your right to walk around the world, everybody might agree that it's better for humanity that you walk around the world, but if you have no legs, then what you want doesn't matter. If you cannot walk on water to cross oceans then what you want doesn't matter.
If there's nothing in the bios to allow all core locked turbo settings, then what you want doesn't matter. 7700HQ is a LOCKED cpu. The motherboard in your Lenovo Legion Y520 does NOT support OC. The Bios on that motherboard is LOCKED and does NOT support OC. Throttle Stop failed because the laptop will NOT allow OC settings.
So wanting OC and getting OC is 2 entirely different things. You can lock all cores a 3.4GHz with Throttle Stop, because that is NOT OC. You can lock all cores at 2.6GHz, because that is NOT OC. You cannot lock all cores at 3.8GHz because that IS OC.
As far as I know, you can undervolt the cpu to increase boost performance, which will raise fps, and you can OC the gpu through Afterburner but the cpu locked core OC is fail.