I have LR4, can I get an upgrade to LR6 or must I buy a completely new LR6 ?
You can buy an upgrade. Go to the Adobe product page, scroll down to LR, hit Buy and select the upgrade.
You will also need this: https://helpx.adobe.com/lightroom/kb/serialize-lightroom-cc-trial-to-activate-as-lightroom -6.html#
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