Buying for older macOS

Hi, sorry if this has been asked before but I finished my free trial and wish to buy but I’m running 10.10.5 on an older macbook pro. For the trial I had to download an older verion of Scrivener. Before I plonk down $45, I want to be sure if I pay for the newest version that’s available, will it still reactivate/register with the older scrivener version I have on my mac?

Also, my macbook is old so I imagine I’ll have to update in the next few years. If I do, will I be able to download the most recent version of Scrivener then at no cost (assuming I pay for it now?) Or would I have to pay again later to upgrade to the newest software?

I hope this makes sense! Thanks

Install Scrivener 2.9 on the older system. It will accept a Scrivener 3 license, and you can then use that license should you update to Mac OS 10.12 or newer in the future.