Seeing the Rolling Stones’ limited, 17-city “50 and Counting Tour” Friday night in Chicago raised more questions than answers. Here are some of them:

What’s the state of the relationship between Mick Jagger and Keith Richards? They seemed to intentionally ignore each other all night except for the exchange of a sly smile during “Sympathy for the Devil” when Jagger sang: “Pleased to meet you.”

Why did Richards seem so nonchalant — or even disinterested — so long? He finally brought the snarl on “Honky Tonk Women,” “Brown Sugar” and “Jumpin’ Jack Flash.”

Why doesn’t guitarist Mick Taylor become more a member than a guest? The three songs on which the ex-Stone (1969-74) played — “Can’t You Hear Me Knocking,” “Midnight Rambler” and the closing “Satisfaction” — ranked as the highlights. His deep, versatile guitar work inspired Richards and the delirious fans. So what if he doesn’t look like a rock star; his musicianship rocked.

Why didn’t the Stones do “Some Girls”? After all, it was two women who ignited the concert: backup singer Lisa Fischer on a roof-rattling “Gimme Shelter” and special guest Sheryl Crow, who sparked Jagger, Richards and Ronnie Wood on “All Down the Line.” She even kissed all three of them and drummer Charlie Watts on the lips afterward.

Has Crow ever been better live? Other guests du jour on this tour have included Lady Gaga, Katy Perry, Carrie Underwood, Tom Waits, Bonnie Raitt, Keith Urban and Taj Mahal, but Crow tore it up like she belonged there.

Does Jagger buy his jeans in the junior girls department? He embodies the notion of “skinny jeans” and gives new meaning to Stick and Stones. Heck, all four of the Stones are amazingly blessed with skinny genes.

Who would win a marathon race between Jagger and Springsteen? Jagger, who turns 70 next month, clearly paced himself Friday but he moved like Jagger for 2 hours and 23 minutes (minus the two songs when he exited while Richards sang) and even danced like Jagger during “Midnight Rambler” and “Sympathy.” But Bruce Springsteen, 63, treats his shows like a series of sprints for more than 2½ hours. I’d pay to watch the competition.

Is Watts more ageless than Jagger? The T-shirt-clad drummer, who turned 72 Sunday, was crisp and consistent, bringing that snap, always finding the pocket, driving the band. Jagger may be the brains, Richards may be the heart and soul, but Watts is the engine.

Why didn’t the Stones play at Xcel Energy Center? They booked three shows (including Monday’s finale) at the 20,000-seat United Center over seven days (and Jagger commented about being displaced by the NHL hockey playoffs in the house that another MJ, Michael Jordan, built). The sound at the cavernous United was muddy; the X would have sounded better.

Why didn’t the Stones call this the “50 and Ka-Ching Tour”? To celebrate their 50th anniversary, the self-proclaimed world’s greatest rock ’n’ roll band charged $600 for top tickets (same price as a Stones leather jacket). A down vest and a jean jacket each went for $100, a baseball cap for $40. By the by, this was the least splashy Stones production since the 1970s: no inflatables, pyro, floating bridges, mammoth erector sets — just a Stones logo-shaped stage with a loop runway for the lower lip and a giant video screen.

Will this be the last time for the Stones on tour? Haven’t we asked that every time since the 1999 tour?

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