Hi Lal,
According to the Paṭhamanānākaraṇasutta (https://suttacentral.net/an4.123/pli/ms) what one experiences in the first jhana is the same for an ariya or anariya. If an ariya or anariya practices the first jhana and dies without its effects decaying (aparihani) then he would be born in the brahma realm.
So tadassādeti, taṃ nikāmeti, tena ca vittiṃ āpajjati. Tattha ṭhito tadadhimutto tabbahulavihārī aparihīno kālaṃ kurumāno brahmakāyikānaṃ devānaṃ sahabyataṃ upapajjati.
This rebirth in the brahma realm is due to the fact that a person “savors that, longs for that, finds satisfaction through that. Staying there—fixed on that, dwelling there often, not falling away from that”, that being the first jhana. This can mean that an ariya who say got to the first jhana one time but did (could) not dwell there often etc., may not be born in the brahma realm.
This rebirth in the Brahma realm (for an ariya or anariya) is due to the gathi of the person and not due to a magga pala. yadidaṃ gatiyā upapattiyā sati.
For an ariya, he does not return to this world and therefore could be called an anagami, however it does not necessarily mean that he has attained anagami pala.
All explanations of first jhana (ariya or anariya) mention viviccha kamehi, viviccha akusalehi dhammehi, which means abstaining from kama. If one can get a kama sanna (which is a hindrance) in the first jhana it means that one has not completely eliminated kama raga. Therefore one doesn’t have to have attained anagami pala to get to an ariya jhana.