The Undertaker Playing Basketball

Yep.
That is the Undertaker, the Deadman, Mark Calaway number 33 playing basketball at Texas Wesleyan University during the 1985 - 1986 season.

And here he is before that at Waltrip High School in Houston Texas in 1983.
Interestingly, that is the same high school that Patrick Swayze went to, although he graduated before the Deadman's time there.

The Undertaker and Sensational Sherri - WWF

Here is a real flashback.
The Undertaker (Mark Calaway) and "Sensational" Sherri (Sherri Martel) from back in the old WWF.