Not Sure about 2nd but will try to answer for 1st and 3rd.
1. L is set of all strings where p <= q <= r and of the form a^pb^qc^r where p is number of a's , q is number of b's , r is number of c's .
Here I think it is not even a CFL as all the strings belonging to this language cannot be accepted by a PDA.
This can be proven using an example . Since the condition is p<=q<=r then all the strings of type p = q = r will also belong to this Language.
Now can a PDA be constructed to match number of a's , b's and c's ?. It cannot be , because if number of a's and b's are matched then the stack would be empty , so number of c's cannot be matched .
Thus we prove that a string belonging to the Language cannot be accepted by a PDA . So this is not even a CFL.
3. Here it is given that p = m +n.
That is number of c's = Number of a's + Number of b's .
For this easily a Deterministic PDA can be drawn .
Just push all the a's and b's and be in a state.
As soon as C is seen , change state and start popping from the stack .
If on reading Epsilon , the top of stack is Z0 then go to final state and string is accepted , else rejected . Thus Language is DCFL.
Not sure about 2nd One