past tense of exist is existed.

Is emerged past tense?

past tense of emerge is emerged.

What is the past tense of lie?

The past tense of lie is lay, but not because there is any overlap between the two verbs. So when you say, “I lay down for a nap,” you're actually using the verb lie, not lay, despite the way it sounds. ... Lied, however, refers to the past tense and past participle form of lie when it means “to make an untrue statement.”