1) Well if youre a left hander sometimes it may be difficult to reach the high frets of the guitar but that really depends on the guitar u play. If youre playing an SG you probably wont have any problems but its not the same when u r using a Les
Paul. Secondly youll have to make changes to the guitar you play. You'll have to change the nut, maybe the bridge and stuff.
3)hammer ons, pull offs, bending is most important and alot of major and minor pentatonic scales (its good to learn all the shapes)
4)that depends. if u r using a lespaul type guitar (or similar) you wont have a problem but if u r using a guitar that has a floyd rose tremolo you'll have to get the help of a guitar tech. When u tune down half step the strings are like this;
from E A D G B e to ---> Eb Ab Db Gb Bb eb . u tune the strings down a semitone.
5) when you do a full bend you can hear the note u r bending (eg A) going all the way up to B and thats it. when u do a full bend with release u do the following; u bend from A to B and then return back to A (you can hear a lot of bend and release stuff at the start of Slash's first solo in November Rain)
hope I helped a bit