If you got money then

Number 2
If got proof sue for them for cheating. Technical term I dont know lar for cheating. Better sue also for compensation of how much you loss like need hire other contractors. Cannot use the house and need to paid rent for existing place.

Number4
Can sue for breach of contract but if you give approvel then cannot do anything since you already give approval for them to claim.

Number6
This the easiest one because no contractor can follow 100 electrical code. If they use non sirim cable these more than enough to sue them. If they max out the piping and trunking till compress the cable then another good point to sue them because there suppose to be if not mistaken need free space 30% . Also if some cable is expose with no piping or they conceal wall directly then another good point.