Sorry not been on here in a while
Answers 1-yes 2 yes 3 no 4 no 5 yes but you have no way to know how long you would have to wait.
Find it very difficult to believe someone got a clause like that in a contract, and anyway they would only honour it if it suited them.
Some IRE/TRE high time guys have walked straight into what they wanted, but they upgrade so quickly these days ( for all positions up to and including IRE/TRE) that new guys coming in might not have the leverage to "negotiate" that they believe they have.
It relly does depend on what day you speak to them and their mood on the day, some get what they want on the day, others wait years and get nothing they want.
It has to be said however, that your attitude and personality can play a big part here.