Yes,you still will be able to pass.
Study hard to earn better grades on future assignments and tests.
In the US: PSAT: 11th grade (and sometimes 10th for extra practice). SAT: Usually 11th grade. PLAN: 10th grade. ACT: Usually 11th grade. AP Tests: 9th - 12th grades.
Yes,5th graders can get good grades. All you have to do is work hard and study. Plus, if you remember stuff for tests, hopefully you'll get a good grade. 
All A+s would be considered grades for a gifted5th grader. There are tests that can be given to test a gifted 5th graders IQ and grade level. Often gifted students will test at higher grade levels.
Beyond having time in grade, you must pass tests and your evaluations.
it depends how many grades in the class you have.
In some states, Standards of Learning (SOL) tests may impact your final grade, while in others they are used for evaluation purposes. It's important to check your school's policy to understand how SOL tests are factored into your overall grades.
California: Math and Science
Every grade is required to complete English and Math tests, but some grades are also required to do science and history (such as 8th grade).
You cannot since grade boundaries may be adjusted to accommodate differences between tests that are easier or harder.
Yes. If you mean that they count the class work as part of the grade, yes. Grades can also be affected by the number of absences, behavior, participation, and tests. Any one of theses things can be a factor in grades.
where can i find sample questions for national achievement tests for grade 3