Could someone please clarify whether the following things make sense while cooking chicken biryani? I've trying multiple iterations to cook chicken biryani like how the restaurants do it. However, after going over various recipes online and trying them out, I'm starting to wonder whether the following cooking steps are inefficient or do they really make a difference, when it comes to cooking chicken biryani.

Here's a sample recipe: https://www.yummytummyaarthi.com/2015/03/white-chicken-biryani-recipe-yummy.html

(Note: The site from the URL linked above has a tendency to get stuck. You need to refresh the page to make it work).

Can anyone throw light on the following points? 


Add spices to water and boil. Add rice and boil till it's 70% cooked. Then drain all the water. Seems like a lot of flavor being wasted there. If all that we want is for the rice to absorb the flavor, then would it make sense to add it while cooking the rice from 70%-100%? O
Marinade the chicken with spices. Then while making the biryani, we start with the base onion layer in which we add the same spices, again! Duplicate work? Does it make sense from a culinary point of view to add the same spices again? Or, would it come to the same flavor if we skip it?
Mixture of spices: Adding saffron-boiled milk (thick milk) + rose water + screw pine extract ("kewra") + fried onions + clarified butter (ghee) + coriander + mint leaves. Keep in mind that we're throwing in these spices with marinated chicken and equally spiced-up sauteed onions that form the base layer. I feel that that's too many spices. What if we choose only one item from saffron-milk, rose water, fried onions and pine extract. Thoughts?
Deep fry the onions. Then pour the remaining saturated oil onto the top of biryani just before sealing it. Does used oil actually add to the flavor noticeably?
Excessive oil? We're adding oil in the following steps: We've added oil while par-boiling the rice. In the chicken marinade. In the oil layer at the bottom. While making fried onions for the top layer. While sauteing onions for the bottom layer. Most biryani recipes call for adding oil at the top. Does it make a difference if we skip that last step?
Air-tight seal: Lastly, there's this step about sealing the utensil with a wheat dough. I feel that that's a waste of good wheat. The idea is that you seal the vessel with dough, then add weight on top of the lid so that it remains "air-tight". How about using a pressure-cooker instead which would guarantee an airtight compartment and then heat it very slow (I'm talking about placing it over a pan that is placed over the stove)? Does this make sense?
As someone pointed out in your last question about biryani, there is a great deal of variation in how the dish is prepared.  However, I will attempt to address your points based on my experience.


Par-cooking the rice is not for the purpose of flavor absorption, but rather so that the rice is fully cooked after the dish is constructed and (in my case) baked in the oven.  I use water only, and add the rice to boiling water, cooking for about 5 minutes, then draining.
In the procedure I use, the chicken pieces are marinated with the spices and yogurt.  Spices are not introduced anywhere else.  When the dish is constructed, the chicken, marinade and all, is added to the layering in the cooking pot.
The spices, herbs, and alliums in my recipe include, garlic, ginger, ground coriander, cayanne, tumeric, a small amount of garam masala, and salt.   These ingredients are added to the chicken, with about 1/2 cup of yogurt.  There is no saffron, rose water, or milk in my recipe.  The chicken marinates for at least an hour, but can sit longer. In constructing the dish before baking I layer, chicken, rice, cilantro, and onions...ending with rice on top and a drizzle of oil.
Correct, as I stated in your previous question.  The oil carries flavor.  It also produces a crust of cooked rice and chicken at the bottom of the pot, which is delicious.
Oil is used once, to cook the onions (in my recipe).  There is no oil in the chicken marinade.  After the onions are lifted out of the oil, I make sure that about 1/4 cup remains in the pot.  After layering I drizzle on an additional 1/4 cup, which was drained from the onions.
My enameled cast iron pot has a heavy cover.  I place a sheet of foil over the pot, then the cover.  It works just fine without having to make a dough to seal the pot. This is then placed in the oven to cook for about an hour. A pressure cooker is unnecessary.