Name the following compounds systematically.

(i): cyclohexene
(ii): 1,2-dimethylcyclopentene

(i): cyclohexa-1,4-diene
(ii): 1,6-dimethylcyclohexa-1,3-diene

(i): cyclohexa-1,3-diene
(ii): 1,2-dimethylcyclopenta-1,3-diene

(i): cyclohexa-1,4-diene
(ii): 1,5-dimethylcyclopenta-1,3-diene