Mobile templates for both Android and iOS

Hello everyone,
Happy new year

This is the first time I am going to have an attempt at building an App for our GPS tracking platform, which we want to build for both Android and iOS.

Are there any templates or themes which have similar appearances for both devices and hopefully can be made simultaneously?

Upon purchasing, Do I need to use an App making application, or does the purchase have it’s own development environment?

Can you recommend any templates for our application please.

Thank you in advance,