Do I need to drive my car set the tyre pressure monitoring system?

After I have adjusted all four tyres to manufactures recommended settings and reset the onboard system, a message appears saying 'tyre pressure registered.' Should I at this point drive the car to set...

Does it matter if one of my tyres has a different load rating?

Due to having had a puncture we now have a 95V rating tyre whereas all the remaining three original tyres are 91V. Is this illegal or dangerous? The supplying dealer says this is causing tyre pressure...

My tyre deflation warning keeps coming back, what could be the problem?

After the warning has been on and adjusting the tyre pressures then resetting the computer I find that after about 20 miles the warning comes back on again. This has happened about 4 times, why?