No they’re not - the first is singular and the second is plural. However, in colloquial Hindi, they are pronounced the same - “ye”. When learning, though, you want to distinguish the sounds.
What about वह and वे? Colloquially, I know the former is pronounced "vo", but is वे pronounced "ve" or "vo" (again, colloquially)?
Because ये is plural. "This is an apple" = "यह सेब है" Notice that हैं differs from है. The former is used in plural and the latter in singular.
This sentence can also be a question depending on the tone. ये सेब हैं ? - In written Hindi, you would have to put a question mark at the end. In spoken Hindi, the sentence would be said with a rising intonation at the end. It would then mean - "Are these apples?"
ये सेब हैं ? = क्या ये सेब हैं ? = Are these apples?
यह सेब है? = क्या यह सेब है? = Is it an apple?
No. If you wanted to pose a question, you would need to put क्या in front of it, so something like क्या यह सेब है?. Additionally, it would not be "an apple" because the verb is हैं, which is plural, indicating that it's more than one apple.