Others can answer too.

I am using the front toolpost, the tool that i want to use is a triangular tip tool.

The way it's mounted in the toolpost it could be used as a facing tool and turning tool

It could also be used as a boring tool over the centreline albeit with the chuck running in reverse.

So would the second description be classed as a rear toolpost setup

Phil

I'd say no.
X values would just be -.

At the moment you need to have all tools designated the same, either all front or all rear so you would if using in the front post either use the G51X-2 and code positive values for the X or code negative values with no X scaling in effect..
In the future you will be able to designate front/rear and what that will hopefully do is autoswap the X axis direction so that all coding will be positive values unless you specifically want and write them as negative values.
Hood

I just tried it, cutting air it worked perfectly.

Just a change of M3 to M4

Phil