Question

#+FollowSymLinks must be enabled for any rules to work, this is a security 
#requirement of the rewrite engine. Normally it's enabled in the root and you 
#shouldn't have to add it, but it doesn't hurt to do so.
Options +FollowSymlinks
#Apache scans all incoming URL requests, checks for matches in our .htaccess file 
#and rewrites those matching URLs to whatever we specify.
#to enable runtime rewriting engine
RewriteEngine On

#this tells mod_rewrite to leave the URL unchanged (the dash part -) and quit 
#other rewwrite processing rules if the requested segment has one of those 
#prefixes (that's what we asking when we use the ^ sign), on the list. If the 
#prefix is in the list, all subsequent Rewrite Rules are skipped.
#So to avoid some files OR directories to be redirected we use:
RewriteRule ^(somefile|somedir|someotherfile) – [L]

1) Don’t we need a condition here before these previous RewriteRule ?

#this will allow direct linkage to this extensions, regardless the case sensitive.
RewriteCond %{REQUEST_FILENAME} !\.(js|ico|zip|rar|mov|mpeg4|mp4|gif|jpg|png|css|doc|pdf|docx|wmv|mpeg|avi|mpg|flv|ppt|pptx|txt)$ - [NC]

2) Will the [NC] flag deal with all case variations here?

#if the request uri has not public...
RewriteCond %{REQUEST_URI} !^/public/.*$
#rewrite to public something...
RewriteRule ^(.*)$ /public/$1

3) Why do we have $1 and not /public/index.php on our RewriteRule?

#rewrite all requests that start with public, to public/index.php and if that's 
#the case, don't run any other rule.
RewriteRule ^public/.*$ /public/index.php [NC,L]

4) since this is the last rule, can we remove the L flag ?

Answer 1

1. No, anything that starts with somefile, somedir or someotherfile will not be rewritten (-). [L] ensures that further rules (including this one) will not be processed.
2. Yes.
3. Because the RewriteCond can match /public/otherthing as well, not just /public/index.php.
4. No, without [L], an infinite loop will occur because the rewritten URL /public/index.php matches `^public.*$.