Complexity Analysis - General Questions

Which complexity class is the fastest-growing among these?

What is the time complexity of this loop?

i = 1
while i < n:
    i *= 2

What is the time complexity of the following code?

for i in range(n):
    for j in range(n):
        total += 1

An algorithm that uses a fixed amount of extra memory regardless of input size has space complexity:

The recurrence T(n) = 2T(n/2) + n solves to: