No. You can not efile a prior year retun. You have to print and mail it.
You just have the right OS to install 2014. You will need a higher Mac OS for 2015 and newer. Mac System Requirements <a rel="nofollow" target="_blank" href="https://ttlc.intuit.com/questions/1899173-minimum-system-requirements-for-turbotax-mac-software">https://ttlc.intuit.com/questions/1899173-minimum-system-requirements-for-turbotax-mac-software</a>