Perform the following tasks using MongoDB queries:

1. List only the first 20 names of companies with offices either in California or Texas, ordered by the number of employees and sorted largest to smallest.

2. Perform the following tasks using the MongoDB aggregation pipeline:

1. Design and implement a pipeline to show the total number of employees by state for all companies that have offices in the United States.
2. Design and implement a pipeline to show the names, total number of funding rounds, and average amount of money raised from funding rounds for companies that have funding rounds data, excluding those that do not. Show only the top 10 by average amount raised.