The first question is, can you change or add fields into the registration form? For example, I don't need telephone number so I would like to rename it to something I will use, in this case school number. Another question, how can I export the registration data gathered for each event into a format that I can print out?

Thanks.

I am totally not an expert, but

1) to rename phone field into something else, you could try to edit language file (public_html/language/en-GB/en-GB.com_icagenda.ini) and change values of
ICAGENDA_REGISTRATION_FORM_PHONE = "Telephone"
ICAGENDA_REGISTRATION_FORM_PHONE_DESC = "Phone number will be used only in case of necessity"

2) is interesting question also for me