Remove php extension with htaccess

Question

I looked here and read the Apache documentation. I just can't seem to get this to work for some reason. I've gotten as far as trying to get it to delete the extension, but it still points to the root directory. I only want this to function in the directory where the.htaccess file is located.

I have three things I need to perform with the.htaccess file.

1. I need it to remove the .php

a. I have several pages that use tabs and the URL looks like page.php#tab - is this possible?

b. I have one page that uses a session ID appended to the URL to make sure you came from the right place, www.domain.example/download-software.php?abcdefg.

Can this be done? Do the links in my header nav include file still have.php once I do this? Should the IE "support.php" link be changed to "support" in the URL?

1. I want it to require the www prefix before every URL, so instead of domain.example/page, it will be www.domain.example/page.
2. I want to get rid of every last trailing slash on pages.

I'll continue to search, attempt, etc. Does it matter whether I'm in a subdirectory?