No, USB4 is a successor of Thunderbolt 3 (but similar enough that it can be backwards compatible with Thunderbolt 3). For instance, Thunderbolt 3 tunnels only PCIe and DisplayPort, while USB4 also tunnels USB 3.x.
USB4 is more of a Thunderbolt 4. Not only can it tunnel USB natively, it seems likely to be supporting a newer higher speed higher than TB3's 40gbps (but if it don't, I'm still happy with 40).
No, USB4 is a successor of Thunderbolt 3 (but similar enough that it can be backwards compatible with Thunderbolt 3). For instance, Thunderbolt 3 tunnels only PCIe and DisplayPort, while USB4 also tunnels USB 3.x.