I want a sample paper of the Karnataka 2nd PUC for my second attempt. I have to score at least 50 mark.

Even if a student fails in pre board exam, he or she can appear for the Class 12 board exam. Model exams help students to know how well they are prepared for the Board exam. A student cannot be detained from appearing in the Class 12 Board exam, if failed in pre board exam. Hence students need not worry, if they fail in pre board. They are advised to prepare well within the remaining time and appear for the board exam. 

Yes, the Karnataka Board usually allows multiple attempts to clear NC subjects. Since this is your third attempt, you should still be eligible. Just ensure you clear it within the board's stipulated period (usually within 6 years). Confirm with your college for specific rules. I will suggest  Focus on preparing well for the supplementary exams.

You will need the details mentioned on your Karnataka 2nd PUC admit card to check your result. Its okay if you have the photocopies of your hall ticket and lost the original one. 

However, it is always advised to keep the documents like Karnataka 2nd PUC admit card secured till the announcement of results.

Students need not apply online for hall ticket, if it is lost. They must immediately inform their school authorities. They will help you with new hall ticket. Students will not be allowed to appear for the Karnataka 2nd PUC board exam without the hall ticket. Karnataka 2nd PUC hall ticket is a mandatory document to carry for the Karnataka 2nd PUC board exams. Students should carry the admit card daily on the exam days. 

No, it is not mandatory to pass the model exam to get the Karnataka 2nd PUC hall ticket. Model exams are meant for students to be familiar with the board exam. Clearing the model exams is not a criteria for obtaining the Karnataka 2nd PUC hall ticket.