Hello,
It's essentially very easy task for me, I will write this class for you in a no time. Basically, I have already wrote BFS and DFS many times, so I have only to write appropriate CLI representation of graphs, and inputs (btw, how should we input the tree, in what format and is it from a file, standard input, or hardcoded?)
I have more than 5 years as PHP developer, and more than 10 years in programming (I was also teaching programming languages, so I can explain you these algorithms if you want).
Now, answers to your questions:
(1) What is the complexity (O runtime) of BFS and DFS?
O(V+E) - V stands for vertices and E for Edges.
(2) What is the difference between a stack and queue data structure?
Stack is LIFO (last in first out), and queue is FIFO (first in first out).
(3) How many hours will it take to do this job?
Less than 1, since I already have wrote algorithms, input and output can take from 30 - 50 minutes to develop.
Contact me for further details.
Kind regards,
Nikola