Istinja' is part of the self purification.
It is needed when there's najasah on your Anus either due to wind or poop. In the given cases your taharah will not be completed without doing it and therefore your wudu' would be invalid. Else it is in best case optional.
Taharah is a pre requirement for reading in the moshaf.
Rinsing the nose in ghusl is obligatory according to the Hanafis and Hanbalis and a sunnah according to the Malikis and Shafi'is.
الاستنشاق ... وأما في الغسل للتطهر من الحدث الأكبر فهو سنة عند المالكية والشافعية، فرض عند الحنفية والحنابلة
— الموسوعة الفقهية
If you are concerned about amoeba contamination then you may consider using a bottle of sterilized ...
In fact your question is a multi-question post which is of a kind that you should avoid:
Your first question mainly is covered in:
How to purify a carpet if I don't remember were the impurity is?:
you must be in a tahir state not your bedding: This means in order to pray your body and all clothes you wear and the surface you pray on must be free from any ...
Before I answer your question let me say I was just like you. So I completely understand what you're going through.
Shaytaan deceives each person in an almost unique way. But the best of his tricks is 'disappointment from Allah's forgiveness'. Allah says when you repent I forgive you. I let you repent because I want to forgive you. Allah says I forgive you ...
If your app will "contain haram ... content", then in what way is it not haram?!?
Are you asking whether entertainment is haram? Not all of it is, some are. People are allowed to be entertained. You will need to vet the content to ensure that it is halal.
"urine" is a najasah (impurity) which has attributes: color, odor and taste.
You should only pray in clothes that have none of these attributes: Your clothes must be tahir (pure or ritually pure) as you would be after perfroming wudu' or ghusl.
The same conditions fo purity apply on the peace of earth or area you are praying on: it must be tahir.