Yes Arupa jhana’s are out there. One can experience them in the human realm. There were two teachers who taught Siddhattha the Bodhisattva before he was enlighten whom had attain Arupa jhana’s. To the Buddha, it was unfortunate that these two teachers had attain Arupa jhana’s and were born in the Arupa loka after they died. The Buddha wasn’t able to pay them back by teaching them the Dhamma.
Living beings in the Arupa loka don’t have the 5 sense faculties. They only have the mind, so they are not able to “read or listen” to the Dhamma. This is why it’s so dangerous attaining arupa jhana’s before attaining magga phala. If one dies during in arupa jhana’s, they would instantly be born in the arupa loka. If they haven’t attained magga phala, they would not be able to learn and contemplate on the dhamma. But if one had attained magga phala and died in arupa jhana’s. Then they would be able to still learn and contemplate on the Dhamma in the arupa loka.
One can become an arahant as a lay person, but they would have to ordain within 7 days or else they would die. Because their attainment would not be suitable for the life style of a lay person.
“In the fifth year after Enlightenment, when the Buddha was residing in the (kutagara) Pinnacle Hall near Vesali, he heard that king Suddhodana was nearing death. He went to the death chamber and delivered a sermon. Having listened to it the king attained Arahantship. As he was too old, he did not join the order but enjoyed the bliss of Emancipation for seven days and passed away, (if a person attains the final stage of Sainthood that person cannot remain a lay person but either pass away or join the order).”
(Note: I’m not the biggest fan of using any materials outside of the Pali canon Tipitaka)
As well it’s not necessary for higher level of seclusion for one to attain higher levels of magga phala (as you can see in the above example), although it would make it much easier.