Theruwan Saranayi!
1. Yes. The duration of the jhana does not matter. As long as one has attained a jhana citta vithi, one has transcended the “kama loka.” Thus the yogi will be born in a Brahma realm. However, in the case of an anariya jhana, that is only temporary, meaning the yogi will return to kama loka at the end of that Brahma birth. But if one has ALSO attained at least the Sotapanna Anugami stage, that yogi will not return to kama loka.
2. The duration of the time does not matter, as explained above. P.S. You asked, “how can one would be in jhana(not samapatti) while walking.” One can be in a jhana with even iddhi powers while engaging in physical activities. It is only in a jhana samapatti that one is unaware of the surroundings; see the post referred to at the end. Note that there is an account in the Tipitaka where Culapanathaka Thero made 1000 copies of himself and worked with them at his temple; see “Are There Procedures for Attaining Magga Phala, Jhāna and Abhiññā?“
3. This is where many people come to the wrong conclusions. Jhanic experience is discussed in detail by the Buddha in “Jhānic Experience in Detail – Sāmaññaphala Sutta (DN 2).”
4. Details on vitakka/vicara and savitakka./savicara at “Vitakka, Vicāra, Savitakka, Savicāra, and Avitakka, Avicāra.”
I just revised the post “Citta Vīthi – Processing of Sense Inputs,” where further details can be found.