The part of speech of computadora is noun, as it means computer in English.
No.
you use the subjunctive the talking about things that aren't facts or certain, like emotions, suggestions, doubt, etc.
for example, if i were to say "yo pienso que tu debas estudiar" (i think that you should study), just because i think you SHOULD study doesn't mean that you actually will, thus making it subjunctive
Hope this helps :)
I can’t help you with the answer if I do not know your phone number, what I can do is spell out the numbers from 0 to 9 and maybe that can help you.
1 - uno
2 - did
3 - tres
4 - cuatro
5 - cinco
6 - seis
7 - siete
8 - ocho
9 - nueve