3.5 SRD and D20 SRD

Can I use these if publishing a work under the OGL (current of future version)?

Or do I have to limit myself to the 5e SRD?

(Example: using creatures in a kickstarter funded published work)

At the moment, best ask a lawyer of your choice.

Indeed

With OGL 1.0a you can use SRD 3.5.

But not the D20 license, which is a different license than the OGL (and frankly I have no idea if it's still active).

When the new OGL comes out, we will see what they do with SRD 3.5 and other editions.