I would supplement Joffrey's answers:
1) Je pensais partir avant 6 heures (imparfait here, passé simple is not possible in this context)
2) In French, we would more naturally say: Aucun étudiant n'aime faire ses devoirs pendant les vacances. "Il n'y a pas de ... qui ..." is not much used in French.
4) Continuer can be used both with "de" or "à". "à" is more common.