Mac keyboard and mouse pad unresponsive after Sierra update

I’m not entirely sure if this has been on another forum but I’ll be putting it here just in case.

I have a MBP mid 2012. It was running on Yosemite when I finally decided to upgrade it to Sierra but after my upgrade, the mouse pad and keyboard suddenly stopped working. The power key was working and the only time that the mouse pad and KB are working is when the MBP is on Internet Recovery.

What I did was I formatted it back to its stock OS which is Mavericks. I tested it for almost a week and the KB and mouse pad worked without any problem. So I tried to reinstall Sierra (thinking maybe the first install had an error) but the problem happened again.

External keyboard and mouse worked fine so I also tried the PRAM and SMC but it didn’t work either.

Put it back to Mavericks again but this time I tried upgrading it to High Sierra but the MBP worked so slow. SUPER slow and the screen was also flickering a bit.

I went to have it checked professionally (not in a Mac store since we don’t have a Mac Store near the area). They said that the cables for the mouse pad or the KB seemed to be fine. They tried what I did but to no avail. They also tried putting in their own hard drive but the problem is still there.

I want to attempt to upgrade it to Yosemite or El capitan but they’re no longer available on the AppStore and I don’t have a bootable USB.

Hey everyone, sorry I couldn’t get back to you sooner. I reverted my MBP to Yosemite and it seems to be working fine. Unfortunately I still can’t upgrade to Sierra or HS without the problems but for now it’s working this way. Thank you for the help though!