Event for player using item, and executing server commands

[AMRAAM]

Hi,

I've created a small server side mod, to detect XP drop events and cancel them, which works like a charm, but now i want to migrate more of my .mcfunction code to a forge mod, the first thing i cont figure out is, detecting when a player right clicks with, a certain item (a default minecraft item with custom NBT,  i would probably only check for the name), and the execute some code, and the other thing, is to execute some default minecraft .mcfunctions/commands from my mod's code, all topics I could find on that concerned older versions, and didn't seem to work anymore.
Oh and also on that note is/how is it possible to modify a players tag-s and scoreboard values from a mod's code?

Tank you for the help I've got excellent answers on my previous post, thanks in advance!