A:Answer You mean to ask:
Does it support Gen 3x4 (answer yes, but at about 2100 MB/s not 3500 MB/s)
Does it support Gen 4x4 (answer no, not 4x4, but it will run a 4x4 at a _reduced_ 3x4 speed)
The 2nd 4 refers to 4 PCIe lanes, which is where this budget machine machine falters. The mobo design (deliberate by Lenovo) will not give you the full 3x4 speeds, you get about 67% read and 50% write of a Legion's 3x4, for example.
Same thing you to insist on using (wasting) a 4x4 NVMe. A 4x4 should hit over 7000 MB/s, but you will only get about 2000 on this machine.