Railways

You can get a free test various in various platforms. On Shiksha you can get a free offical mock test ;

From this you can prepare for your upcoming exam.

Link https://www.shiksha.com/exams/rrb-group-d-exam-mocktest

Candidates after Class 12 can apply for RRB NTPC, Group D exams. The eligibility criteria for RRB NTPC Undergraduate post is that candidates must have passed Class 12. For Group D exam, candidates must have passed Class 10 (High School) and have National Apprenticeship Certificate (NAC) granted by National Council for Vocational Training. Candidates who have passed Class 10 and ITI are also eligible for the exam.

No, basically Admit card would be recived only once after the full payment is done . Which includes both the application fees along with modification fees . 

Your admit card would be visible once you completely pay the fees,  

You can only modify the application details after paying modification fees, once after the payment you can apply and get fhe admit card .

If you lose 1/3rd of your index finger on the right hand, then you will depend upon the specific medical standards formulated by the Railway Recruitment Board for the specific position for which you are applying. Generally speaking, all applicants are expected to have some standard level of physical fitness, including limbs functionalities. For most posts under C-2 medical standards, for example, candidates are expected to be fit in all respects. It is also wise to check the detailed medical standards by the RRB for your post and seek a medical assessment if need be. 

The last RRB NTPC exam was moderate in terms of difficulty level. The General Awareness section was moderate, while General Intelligence and Reasoning sections were easy. The overall difficulty level of the Mathematics section was easy to moderate. RRB NTPC exam is held for 90 minutes for general candidates while 120 minutes is given for PwBD candidates. The standard of RRB NTPC syllabus has been basically based on Class 10, 12, and graduation levels.