Improvements to construction estimating Excel Spreadsheet

Please see the attached spreadsheet, it should be fairly obvious how it works, it's for estimating costs for small construction projects. I'd like help implementing the following changes/improvements.

1. I'd like to be able to easily add additional lines correctly formatted without having to copy the formulas. Maybe a button to add more lines

2. I'd like the "Task" cell to be a dependant drop down list from the "Build Stage" - I've started the "Task Table" tab which shows with task is in each build stage. I'll be constantly updating this list on each quotation so the task list should be very easy to add to.

3. I'd like to implement filters on the "Area" and "Build Stage" columns so that I can easily resort the columns without having to select all the data.

4. I'd like a client view tab that shows the first 6 columns only - so they can't see the cost or markup.

So for a new project quote I'd be able to do the following process:

1. Populate the client / address / date / area list / markup / error margin /
2. Add lines for tasks - This would be fairly randomly either by Build Stage or Area
3. Easily re-sort the Area/Build stage as I add tasks.
4. Easily send the client the quote from the client view

Ideally I like this to work on Google Sheets - If there are some functions that make it better that are Excel on then that is fine to.