The focal budget has been given to each manager, so will the manager decide how much hike he will give to each employee or is it a mutual discussion with the manager and director?
Each BU gets a bucket of money, and the BU SVP will have to divide it among their VPs, who have to decide how to split it between their Sr Managers (if any), who then split it between Managers, who then split it between employees.
Sometimes managers or sr managers will go up the chain for a bigger piece of the pie if they feel that they have an employee who deserves more than their allotted bucket allows, but that's at the cost of someone else's bucket within the org, so there's a lot of mutual discussions up and down the management chain.
and after 1:1 discussion can the manager change the hike percentage or promotion ?
Usually, by the time the manager has the 1:1 discussion about your IPF, it's cut in stone and you're being notified of what the changes are and when they will go into effect, or so that's been my experience.