NATA Scores

Yes, you can get admission for Architecture course.

Looks little difficult without clearing Diploma.
Visit this link to check B.Arch colleges based upon your rank:
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor?utm_source=connect&utm_medium=CR_JEECP&utm_campaign=6919840
Then visit this link for various colleges which provides you brochure:
https://www.shiksha.com/architecture-planning/colleges/b-arch-colleges-india

You are qualified in NATA and diploma for admission to Architecture course. If you are looking for a government seat, then you may submit your marks card to Government counseling office, based on which they would give you a rank card, and you may choose colleges of your choice, college allotted will be based on your rank.

It is little difficult, but yes you may try. Visit this link to check B.Arch colleges based upon your rank:
https://www.shiksha.com/b-tech/resources/jee-mains-college-predictor?utm_source=connect&utm_medium=CR_JEECP&utm_campaign=6919840
Then visit this link for various colleges which provides you brochure:
https://www.shiksha.com/architecture-planning/colleges/b-arch-colleges-india.

You have to be qualified in NATA or IIT JEE part 2 for admission into Architecture course.

Sadly no, either you have to be qualified in NATA or IIT-JEE part 2.

Yes, you have very good chances in both the colleges.