Looking to develop an add-on to our Shopify Website and Migrate Store to a new Theme with new Features

Part one Add-on to Shopify Website (App):

We delivery healthy food (www.greenpress.com.pe). We currently use two Shopify apps: 1- "Local Delivery" (https://apps.shopify.com/local-delivery-1) so users can select a date and time frame for delivery and 2- We have developed another app ("Apolo" – which is hosted on our server) that charges a delivery cost depending on delivery location and items purchased. We want to add new functionalities and improve the current ones in a new app that replaces both previous apps.


To summarize the new app will have the following features:
1.    Allow customers to choose delivery dates and hours (have an option for immediate delivery that we can turn off manually or automatically based on the day/hour) or choose to pick up the product (which we can turn off or on).
2.    Charge a delivery cost based on the amount purchased, the items selected, and the place of delivery (our current app Apolo already has this functionality, we just need to integrate it).
3.    Allow us to set how many days/minutes before a customer can make a delivery order based on the products they have selected and have an inventory that we can update manually and automatically to track products so they become unavailable for delivery on the same day if they ran out of stock. Also shows on the product page and collection how many are left of that product for delivery today. Take into account that some “products” are packages composed of other products, this would have to be taken into account to calculate how many of these packages are left.
Allow us to prohibit the sale of certain products on certain dates.
4.    Create a pop up after adding to cart that gives the option to continue shopping (that bring you back to the last catalog you were browsing) or go to checkout

Part 2 Migrate Store to a new Theme with new Features:

On the home page show the different collections in a table format and when you mouse over the picture fades and shows a summary explaining and you can click to see more or purchase.
2.      Have a filter option similar to this site https://www.snapkitchen.com/menu/category/lunch_dinner? Also have a filter by price (low to high)

3.      Have the option to favorite dishes (if you are not logged in it will ask you to do so in a pop up) so you can also open a collection of your favorite products.
4.      Show the calories and price directly on the catalog.
5.      Allow to add to cart directly on the product catalog (if there are variants show them so they can choose) and it lets you know when you have added one.
6.      In the product page the picture of the meal stays on the left side of the screen (for desktop).
7.      Have an interactive chart (that can be turned on or off by the admin depending on product) with nutritional value. Example: https://www.snapkitchen.com/menu/product/bison-quinoa-hashtm/4177758
8.      We will also offer meal plans (for especial diets) that have a prefixed menu per day.
Have a page template that is easy to update with the upcoming meals (breakfast, lunch, dinner, snack, etc).
9.      Show a suggestion of sides and snacks to add (at the end of the page and when you go to  your cart).
10.  At the cart page it shows a text based on the products selected (there will be some explanations regarding the product and delivery.