What are the other clearance and instructions that must be read back? The following items must always be read back:


ATC route clearances;
clearances and instructions to enter, land on, take off from, hold short of, cross or backtrack on any runway; and
runway-in-use, altimeter settings, SSR codes, level instructions, heading and speed instructions, and, whether issued by the controller or contained in Automatic Terminal Information Service (ATIS) broadcasts, transition levels.


In the definition it goes on like this: Other clearances or instructions, including conditional clearances, must be read back. What do I have to obtain from these "other clearances or instructions" I think it is the really broad term?
Generally speaking, you should read back all clearances, instructions and warnings. You may in some cases not need to read back information, unless it is safety critical (for example QNH).

One of the only instructions I can think of that you do not need to read back is an instruction to report something (report passing 5000 feet, report established, report overhead XYZ). A proper reply to an instruction to report something would be "WILCO". But in all other cases, if ATC directly instructs you to do something, it should be read back.