Build a Shopify App

I would would like to build a Shopify app with the following features.

I am a bit new to this but I know exactly what I want and what my budget is.

So I am looking for a capable developer, preferably with experience building Shopify apps to work with.

Based on the requirements below:
Automation Flow Page
Welcome Flow Page
Browse Abandonment Flow
Shipping Notifications
Back in Stock
Price Drop



Tell me,
-How long it would take to implement these features from scratch (UI will be provided)

-Also, which tools stack/language(s) will you use?