Track pad and plug-in mouse left click not working I've searched and noticed other people having the same issue but no fixes.

Recently my trackpad stopped working which resulted in me changing it.

Worked fine for months. All of a sudden my trackpad left-click stops working and even if I plug in a mouse, it doesn't work, but the right click on the plug-in mouse works fine.

The left click works fine in Diagnostics mode, works every time. But works nowhere else. 

I thought I would reinstall the OS to see if that would fix it.... but now I cannot install the OS as I get stuck on the page where you have to click the Hard drive and press next, can't seem to do that with the keyboard only.

Any suggestions? Need to work from home and can't get it working. 
Model A1502 Macbook pro
Thank you.
I would recommend splitting this question in 2 since you had 2 different issues even though they are affecting each other. 


First one (this post) would be to only figure out how to reinstall OS with just keyboard. Take some pictures with your phone and post them along with your question so we can help you better. 
If your input hardware doesn't work even after the OS re-install, post your second question with the new post-OS-install details.


As for your hardware, have you tried using tab and shift + tab to change focus (indicated with a blue boundary) and use spacebar to select that button, while enter only works for the button filled entirely with blue colour.