Account sharing PS4: Can I play on the secondary account if the primary account PSPlus also has their PSPlus games?

So my roommate and I both have a PS4 and we share the accounts, I would buy his account now for PSPlus for the year, but my question is can I also play his PSPlus games on my Acc? I know that I can then play online and everything, but I can also play his PSPlus games. Please only answer if you are 100% sure.

Yes it is the same ps4 you need more help or just ask.

Well he also has a PS4, let's call him C: C has his main account on secondary on his ps4 and mine as primary in order to be able to play my games with him. I have C's account on primarily to be able to play his games, we have been sharing the accounts for a long time, always works. The question is, if I play on C's Acc PSPlus whether I can play PSPlus on my PS4

You would have to download the ps + game via its acc and then start it on your acc