is it possible to tune to drop-d with a LFR? because i want to play some Tool but idk if I can drop tune with my guitar. And the LFR is an Edge III
First off, what kind if guitar do you have? Second, yes you can detune a tremolo guitar from EADGBE to DADGBE without any problems. Just unscrew the nut for the E & A string and de tune the E string down to D. I've seen this done quite a few times.

Hope this helps.
You can, but you'll have to mess around with the springs in the cavity in the back to get the correct tension. If you want to have your guitar in drop-D for some period of time, go ahead, but if you're planning on going back and forth between drop-D and standard, my suggestion is not to do it. It'll be too much of a headache.
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It's not really that hard, just unlock the nut. Tune your guitar to Standard with the low E strings fine tuner almost all the way tightened. Lock the nut then loosen the fine tuner and it should drop to D. NBD
FR's are awesome, but they have their problems as well. Not being able to tune down in less than twenty minutes is one of them. Recently I saw an EVH guitar with an FR that included a special tuning system that allowed instant Drop-D tuning switches, but normal FR's are terrible. Loosen the nut bolts, retune with the tuning pegs--I assume you know how to tune with an FR, seeing as you own one --and then tighten the screws in the back a bit. Put the nuts back on and hit the whammy with a few dives and light pulls. Check your tuning. If you're flat, tighten the screws; if sharp, loosen 'em. Repeat as needed.