(1) I wish (if only) + Past Simple: wish about present
(2) I wish (if only) + subject + could + bare infinitive: wish about the present
(3) I wish (if only) + subject + would + bare infinitive: wish about the future
(4) If only means the same as "I wish" but it is more emphatic.
(5) After "I wish" we may use "were" instead of "was" in all persons.

Two nice episodes of Phineas and Ferb. As always. No spoilers.

Phineas & Ferb: Lights, Candace, Actions - Wishes All Tenses

phineas-ferb-lights-candace-actions-wishes-all-tenses

Let's do English ESL general grammar practice. (1) I wish (if only) + Past Simple: wish about present
(2) I wish (if only) + subject + could + bare infinitive:…