"1) Family is setting out for a day out at the zoo or similar. Four year old has a tantrum and get's angry and hits out at sibling or parent. Would you continue on your day out, or would you think it appropriate to cancel the day out, or even just make the offending child stay at home with mum while dad and the others go on out. OR would you deal with the tantrum issue, talk to the offending child and issue another consequence, such as not having an ice cream out, or no TV when they got home etc...."
IF the family contains a sibling and you cancel a day out, then that means the sibling is being punished for being hit. I would never devise a punishment that affects an innocent child.
And I wouldn't make a massive deal out of a 4yos tantrum either.
"2) Four year old has been naughty and sent to room for time out. While in his bedroom he settles down and starts playing with his toys/reading books in his bedroom. Do you think that this is okay, as at the end of the day, he has been removed from the previous situation where he was being naughty, and as long as he is being quiet and 'calming down' it is ok. OR would you try to make the child sit on his bed, and play with nothing and just think about what he has done wrong?"
You tell him he has to stay in his room, then find he copes well with it- so you give him a further punishment, moving the goal posts? No, no, no, no, no. If I have said "this is the punishment for X", then that is what happens. (Imagine a judge saying "Prisoner X has been so quiet and well behaved in prison that we will lengthen the sentence by 10 years"- it just goes against all ideas of natural justice).
"Also, how long would you say was appropriate for a four year old to have time out in his bedroom? Would you say all of the afternoon, if he had been so naughty for example, hitting. Or would you say, 5-10 mins until he is ready to say sorry."
A minute per year sounds good to me. And some children can never bring themselves to say sorry, so you could end up being at loggerheads throughout their childhood.
"Also, would you be able to move on from an incident and enjoy the rest of the day, or would your emotions over ride you, making it difficult to enjoy the day / forgive and forget the situation."
I don't see the need to take a 4yo tantrum that personally- they are only children and are still learning self control. I am not on their level.