I'm a little bit confused by the phases of the first challenge. Does the "final phase" mean, that I will no longer be able to get metrics on the validation set between the 1st and the 15th of April? Or is this just the date, at which evaluation on the test set becomes possible?
The most important question is - will there be any limitations introduced after the 1st of April, or nothing changes basically?
No you will still be able to submit your results on validation set, so the Development and Feedback phase continues until 15th of April as well. As you said, it is the date that you can evaluate your models on the test set.
No nothing changes, only for the test set there will be limited submissions but that's all.