1. Unluckily, Flight service does not yet supported with woocommerce booking. We are working on to update it.
2. That is default option for car. There is no option to change it.
3. We are working on to built new feature for traveler named Car Transfer.
Currently, you can use Custom search form for all services to create transfer (car type)
4. You can go to Traveler Settings > Activity Options > Activity Search Fields > check the Require option for activity date form.
If it enabled, user can not search activity without select date.
5. Currently, you can use custom sidebar to create a sidebar in checkout page but theme does not widget to display related service in check out page.
6. You can select your main language of site in Settings > General > Site Language. ALso you can use WPML for your site language and using poedit to translate some special work on theme.