ram optiplex 9020 ddr3

my ram recently has been dying and i want to replace it but the only ram that i have to replace it with is ddr3 ram. The cpu in my OptiPlex 9020 is the i5-4590 which according to my research means it is only compatible with ddr3L ram (i think). So my tow questions are:

1. is this correct that my current pc is not capable of using ddr3 ram? or is it something else preventing me from using it?

2. because i already have 16 gb of ddr3 ram in my garage, i was going to upgrade the cpu to the i7-4770 if that would allow me to use the ram. 

i am now realizing that the i7-4770 is also a 4th gen proccesor and there for would theoretically not be able to run ddr3 ram (only able to run ddr3L). that being said i have heard that other people are using ddr3 ram and i can not figure out why the ram would not work in my pc, but it would work in theirs. 

if you can help, i want to say thank you so much