Though it does not explicitly call this out in the book, a martial adept may not ready a given maneuver multiple times. Each maneuver slot must be filled, and each slot must be filled with a different maneuver. This is CustServ's clarified position on the matter, and it seems sensible because otherwise there would be nothing preventing a high-level martial adept from simply readying his highest-level maneuver in all available slots.
Minimum initiator level is considered a prerequisite for any maneuver, even if that maneuver does not have any other listed prerequisites. Thus, it is impossible for a 1st-level fighter to take the Martial Study feat to gain Mountain Tombstone Strike, as Mountain Tombstone Strike has an implied prerequisite of Initiator Level 17 (see Bo9S p39, "Selecting Martial Maneuvers").
Strikes that also provide healing or some other benefit for the martial adept or his allies do not function unless the strike component is initiated on someone who is hostile to the martial adept. Allies and members of the same party cannot be considered hostile to one another no matter what the players' actual attitudes towards each other might be; see NPC Reactions and Attitudes for further details. This ruling is to prevent players from "pretending to be hostile" or otherwise initiating strikes on their nominal allies in order to gain benefit of unlimited between-combat healing.