1. Is there a ban on donations from foreign interests to political parties?

Hungary
Answer
Yes
Source
Parliamentary Elections, 8 April 2018 ODIHR Limited Election Observation Mission Final Report
https://www.osce.org/odihr/elections/hungary/385959?download=true
Comment
The Law on Party Finance of Hungary prohibits donations from companies and foreign individuals or organizations.