I don't think anyone will know what brake arms you're talking about if you don't give model numbers. There could be several different models in the same "Deore" or "Alivio" name.

The current 2019 and 2020 catalog only has these trekking brakes with 107mm lengths.
BR-T610 ($15)
BR-T4000 ($10)
https://productinfo.shimano.com/#/sp...ke%20(V-BRAKE)

There is a shorter "mtb" version with 103mm length.
BR-MX70 ($30)

And a mini road version with 90mm length.
BR-R353 ($15)

Meanwhile some shops seem to sell another model that isn't in the Shimano catalog, called:
BR-T780 ($30)

I have the BR-T4000 ($10) and it works great. The only problem I had was that the brake boss on my bike was for the stock Tektro brakes, which had a different shoulder height, so I had to make some spacers to get the BR-T4000 to install all the way onto the brake boss. The BR-T4000 works better than the stock OEM Tektro brakes that came with my bike.

I've never used or seen the other Shimano brake models, but they all look very similar. If there's any difference other than the color and finishing of the arms and the different pads that come with them (but I use my own pads anyway so what comes with the arms doesn't matter to me), perhaps the material or design of the pivoting parts are a little bit different.

Also, if you did a 1 minute search on Google, you would have come up with an older post about the same question:
XT T780 vs. Deore T610 vs. Alivio T4000 V-Brake Armageddon!

Also, I don't think there is a difference between front and rear packages, other than the direction of the brake pads. If one is cheaper, you could probably buy 2 pairs of the same package and simply swap the brake pads to opposite sides on one of them.