Compatibility with motherboard and graphics card pci

1st theme
is wrong to connect a graphics card with pci v2.0 on a motherboard pci v3.0
it is compatible ?
it won’t work? or what can i do?
Nvidia Quadro K4200 in a Gigabyte GA-X79-UP4
and which processor should i use ?

2nd theme
if i have a processor i won’t need a motherboard?
which is the right architecture of a pc?

Which mother board would be better for an nvidia quadro k4200 and a processor i7 4th generation?