In my airline, when it is the F/O's sector:
• I sign the Tech Log and the Loadsheet.
• I make the "Welcome Aboard"
PA to the passengers.
• I may call "Stop" for any
malfunction below V1.
• I decide if an emergency evacuation is necessary.
• I do the landing in limiting cross-wind conditions.
• I autoland in Cat 2 or Cat 3 weather.
• I taxy the aircraft onto the gate if using AGNIS.
Other than that, roles (but not seats) may be fully reversed, with the Captain still retaining ultimate authority and responsibility. The law says you can't give that away!
F/Os start engines, taxy the aircraft, reject take-offs for major malfunctions, fly engine-out approaches, land on limiting runways and deal with any problems that may arise.
Of course, F/Os vary in their level of experience and ability, and obviously we use our discretion when deciding which sectors to give away, and to whom, but the SOPs remain the same.
A low hour F/O, just starting in the company, unfamiliar with long haul and new to the B747 would not generally be asked by a Captain to handle the more demanding sectors, whilst an experienced F/O, who may be about to do a command on type, should be able to handle any sector.
In my view, if you do not regularly perform a task, then over time you will gradually loose competency in it, next you will become unable to monitor it effectively and eventually you will forget how to do it at all.
Role reversal helps to prevent this, and, as far as is possible, should be encouraged.
I have been a Captain on an aircraft which did not have a P2
tiller, and did not like the handing over/taking over of control whilst moving on or off a runway. It has the potential to go wrong, and should be avoided where possible.
If you don't trust your F/O to taxy on and off a runway, he shouldn't be in the seat at all.
250 kts below 10,000', where allowed, should not present a problem, and I can't see any reason for it to be prohibited. It was very useful on a previous type I flew, where 400 kts in the LHR
TMA did save a lot of fuel.
That said, it often doesn't save as much time when inbound as some people might think, and I suspect may be imposed by companies simply to try and prevent rushed approaches.