you can lock up both the front and rear, yes. there are plenty of options for it.
for me, i thought fully locking the front was a little dangerous (and expensive)
i didnt want to start shredding cv axles if i ever got the thing really buried. the limited slip i picked out for the front seemed to be a good compromise, though some people would warn against it. i wish i had been able to install and test the eaton truetrac but it just never worked out that way. coming from my 14 tacoma offroad, i knew what a difference a rear locker made... i was actually shocked to learn the 3rd gen 4runner didnt even have a limited slip in the rear! i took it a few places i wouldnt have had i known i was running open difs. miss that truck but my 14 TE is just tits.
i highly recommend installing at least a rear locker if youre going to be getting yourself into some fun stuff. open difs suck!
if you want that stock look for future resale or just to have that stock look, feel free to come take this axle off my hands