When to double the last letter + ed?

When to double the last letter + ed?

(1) In general, add - ed at the end of the verb. For example: work - worked, want wanted (2) the verb ending in silent e, directly add - D. for example: Live - lived, hope - hopped (3) the verb ending in "consonant letter + Y", change y to I, and then add - ed. for example: Study - studied, cry