Modification to iOS and Android App

We currently have an app (Report on the Go) that is available on both Android and iOS. The app is an action tracking tool (create an action, assign it to someone, and they close that action) and is mainly used on construction projects to identify errors and correct them.

I have 3 modifications I require to do to the app:

Modification 1: To set up advertisements using Facebook Ads and Google Ads and optimize for those ads, we need to install some code (SDK) in the app to track actions.

Modification 2: Currently if a group is selected, the responsible person that is assigned can only be from the user list. I would like to add the option that the responsible person can be a custom entry (see attached photo)

Modification 3: Currently, observations can only be closed out by the responsible person and admins. We need to make it so that anyone in the group is able to close out the observation.

I have a lot of modification work to do for the app and so this job is sort of a test job. The Freelancer I am looking for:
1) Prices fairly
2) Gives his projects attention and time
3) Can work on both android and iOS

Please include in your quote a list of things you need so that I can get them from the previous developer.