.htaccess redistribution between 3 index files, why doesn't it work?

Question

htaccess

The task is not solved in any way:
There are three sections with index files on the site, it is necessary that:
1) when accessing the directory "a" (at the root), a redirection to the file "c/a/auth/index.php" occurs
2) when accessing the index file of this directory worked for the "b" directory, and everything after the domain name was written to the variable
3) all other requests went to the index file at the root, and everything after the domain name was written to the variable

My version:

<IfModule mod_rewrite.c>
 Options +FollowSymLinks
 RewriteEngine On
 RewriteBase /

# /
 RewriteCond %{REQUEST_FILENAME} !-d
 RewriteCond %{REQUEST_FILENAME} !-f
 RewriteCond %{REQUEST_URI} !(.pdf|.php|.phtml|.html)
 RewriteCond %{REQUEST_URI} !(.*)/$
 RewriteRule ^(.*)$ $1/ [R=301,L]

# a
 RewriteRule ^a/$ /c/a/auth/index.php [QSA,L]

# b
 RewriteRule ^b/(.*)/$ /b/?q=$1 [QSA,L]

# c
 RewriteRule ^(.*)/$ ?q=$1 [QSA,L]
</IfModule>

What's wrong?