Statistics...

1. no, because you cannot solely depend on the r value to make this kind of statement.
the choice of model depends on a lot of other things,
such as the nature of the data, the usual relationship, the nature of the trend etc.
2. This may allow the student to make accurate predictions, if the prediction is within the range of the data, however, if the value we want to predict is outside of the range, then the prediction may not be accurate.