Does it matter what two factors you select to complete a factor tree? And tell me how you knew

No. as long as you factor out until you get to numbers that can't be factored you're fine. For example if you're factoring out 36 you can start with 18 and 2 or 12 and 3 or 4 and 9 and still end up with the factorization of 2•2•3•3

No, just keep factoring until you cannot factor any further.

example:

90

.^

9*10

^ ... ^

3*3*2*5

I could also start with 15*6, 3*30 or whatever. but the final answer will still be

2*3*3*5 = 2*3^2*5.