#1
Would it be easier and more useful to practice certain techniques on acoustic guitar and then switch to electric guitar?
#2
Definitely learn techniques on acoustic. Yes, it's harder, but that's better. Once you can get the techniques down on acoustic, you can play them flawlessly on electric because electric guitars have lower action and string tension than acoustic guitars.
#3
yes...it is harder to do things on the acoustic, so practicing techniques on the acoustic then transfering to electric is best... i actually have a classical, so the neck is much wider than my gibson les paul...which is good because if i can play a riff on my classical, then i can play it on my electric...

also main riffs that i create all come from my classical and then i just transfer it over to my electric...and i play in a metal band