Is attaining to Jhana possible for me? I searched for the word 'Jhana' on this site and read almost all about 50 odd questions on Jhana. I asked few questions myself.
It seems like one has to put extreme efforts to attain to Jhana.
This is part of one of the answers;

...They sit 12+ hours everyday for many months or years to get this light
which can shine in their mind trough the dark night. It is shining
breathe or meditation's object, not sunlight. Today, many of them have
not been laying on a bed for 20 years...

This isn't practical for lay disciples, or at least for me outside of retreat. At this point Jhana feels like a wishful thinking.
Should one aim for Jhana in sitting?
If not Jhana, then, is there any other state to aim as an intermediary to Nirvana.
I do a daily 90 minute sitting and some chanting. Is it possible for me to attain Jhana?
What is recommended daily duration?
I think you are misunderstanding the nature of jhanas. In your defense, this is a mistake made by almost everyone on a certain stage.
You think jhanas are some concrete states that are specific and can be recognized, that all people must go through same exact experiences on their way to nirvana/enlightenment. That the final Liberation is also something very concrete. Alas, those are all wishful simplifications.
Real-life experiences are a lot more fluid and variegated. That's one, and two, as you get more and more enlightened you realize more and more clearly that labels are mere labels and that in real life everything &quot;it depends&quot;.
So, the jhanas are not something mighty specific that can be entered, that's bullshit (pardon my language). Jhanas are approximate phases in your mastery of your emotional intelligence, mastery of mind. You don't sit for 12 hours straight staring at the wall and then boom! you're in jhana, no. Instead, you must learn to analyze and condition the state of your mind.
Specifically, you learn what makes you sad and glad, and how to make yourself joyful and motivated. You discover your inner pre-logical core and learn to reconnect with it. You learn to puncture through noise of thoughts and into the inner clarity. You discover first-hand how your mind's association and interpretation circuitry works. You master the connection between your interpretations and your emotions. You understand the power of context, the power of comparison, the role of reference point in evaluation. You learn to juggle contexts. You can freely enter and exit the contexts of other people.
Mastering all this makes you very even-handed. You are no longer carried away by your emotions. First, you have to apply effort to keep your emotions steady and stable in the moments of frustration or challenge, but with time you get rather steady even without much effort, things don't disturb you as much. You can go through difficult life situations without getting overwhelmed.
Because you are no longer overwhelmed by your emotions and no longer bounded by your mental contexts, you are not obsessed with your problems, you can actually see and hear other people's problems from their sides.
Then eventually you get to the existential questions like the meaning of life, the death, the happiness and suffering, karma - and you begin to see it rather clearly. It gets pretty clear, how things work.
That's what this training is about. You don't have to sit until your ass falls off. The point is not in sitting, it's in what you are sitting about. Mental and emotional untangling. And half of that work (if not more) is done off the cushion.
It is serious, hard, non-trivial, but deeply rewarding, process of discovery and mastery. Not some childish fantasy. But in the end it's much more cool - and real - than any fiction.
So the First Jhana, is when you learn to make yourself joyful at will using auto-suggestions, recollections, deliberate thinking on appropriate topics. That's it. Magic!
The Second Jhana, is when you can do the above then stop and keep joyful and energized, optimistic and confident without the auto-suggestions, for as long as you stay awake that day.
The Third Jhana is almost same as above but more refined, without the show-off marching parade function of joy. You can stay lucid, calm, emotionally sober, peaceful, harmonious - all day long, without auto-suggestions - just by maintaining your inner balance.
And the Fourth Jhana is pure judgement-free awareness. Whatever is going on, externally or internally, you can stay judgement-free, not qualifying any experience as good or bad. Unperturbed, immovable like a mountain. Clear like water. Transparent like space. Everything is just the way it is, and not a tad different.
This is all real - and practically useful - stuff, not sitting and wishing for some fictional inner sun to shine.