Can I run two tests simultaneously with the same start point, but different end points?

Yes, with a few conditions…

Multiple on-page tests

You can run multiple on-page tests, and as long as you aren’t overlapping content your results will still be perfect.

Nesting tests – having a test row with a test element inside the row, will work, but your results will be incorrect.

An on-page test on a Full Page Test

Not recommended, but you might get away with it if you’re only testing on variation pages, not the start page.

2 x Full Page Redirects

You can stack multiple full page redirects, BUT ITS RISKY. As the page redirects a few times leading to a bad user experience and Search Engines can get grumpy with you also.