Answer 1

Publishing on the App Store is expensive, $99/year. I’d start with Android if I were you. $25 once.
For Android:
https://www.sololearn.com/Discuss/717086/?ref=app
https://www.sololearn.com/Discuss/761432/?ref=app
https://www.sololearn.com/Discuss/488976/?ref=app
https://www.sololearn.com/Discuss/882863/?ref=app
https://www.sololearn.com/Discuss/688949/?ref=app
https://www.sololearn.com/Discuss/622803/?ref=app
https://www.sololearn.com/Discuss/285352/?ref=app
https://www.sololearn.com/Discuss/823823/?ref=app
https://www.sololearn.com/Discuss/311752/?ref=app
https://www.sololearn.com/Discuss/914055/?ref=app
https://www.sololearn.com/Discuss/237742/?ref=app
https://www.sololearn.com/Discuss/987969/?ref=app
https://www.sololearn.com/Discuss/1014498/?ref=app