Hello 
Thanks for your questions.
For question 2:
Check out this guide on how to add bulk submissions https://github.com/common-voice/common-voice/blob/main/docs/SENTENCES.md#bulk-submission.
For question 3:
We ask that you validate a sample of the sentences. This post explains how the Europal Dataset with Speeches from European Parliament were validated: Using the Europarl Dataset with sentences from speeches from the European Parliament
If you have any questions, we are happy to help.