Fill in the event title, date, start and end time, location and description, choose a timezone and reminder, then download the .ics file or copy the raw text.
Yes. The output follows RFC 5545 with the required VCALENDAR and VEVENT blocks, CRLF line endings, a unique UID and a DTSTAMP, which is exactly what those apps validate. Attach it to an email or import it from the calendar's settings.
Choose UTC and the times are written with a trailing Z, which every client interprets identically. Choose a named timezone and the event is written as a floating local time with a TZID, so 10:00 stays 10:00 for attendees in that zone.
Yes. Pick a reminder interval and a VALARM block is added with a DISPLAY action and a negative trigger, so the calendar app pops a notification that many minutes, hours or days before the event starts.