Here in the US, passengers cannot access the cockpit jumpseat like some can elsewhere in the world.
As far as touching the controls goes, here's the US FAA reg:
"Sec. 121.545 Manipulation of controls.
No pilot in command may allow any person to manipulate the controls of an aircraft during flight nor may any person manipulate the controls during flight unless that person is--
(a) A qualified pilot of the certificate holder operating that aircraft.
(b) An authorized pilot safety representative of the Administrator or of the National Transportation Safety Board who has the permission of the pilot in command, is qualified in the aircraft, and is checking flight operations; or
(c) A pilot of another certificate holder who has the permission of the pilot in command, is qualified in the aircraft, and is authorized by the certificate holder operating the aircraft."
I'm certainly not an expert on every country's own regs, nor every airline's company policy, but I'd bet that they have similar prohibitions.
For a sobering example of what can happen when a non-qualified person is occupying a pilot's seat in-flight, see the site below. Note the effect of the 2-second delay.
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.