PS Elements 18 compatibility with MB Pro 13" mid 2009 (OS 10.11.6)

Hi,

I would like to know if PS Elements 2018 is fully compatible with MB Pro 13" mid 2009 (OS 10.11.6).

I have installed the trial version; I noticed slowdowns in El Capitan.

Can I buy older versions? I have PS Elements 10 registered, but it doesn't work with El Capitan.

Can I upgrade to later versions more compatible with MB Pro mid 2009?

Thanks in advance

Joe