Disallow robots - .htaccess & robots.txt

[Zia]

helo...
as we know we can control bots/spider using robots.txt

we know to disallow bot we use
we use:

User-agent: BotName
Disallow: /

but to allow any particular bot for all places can we use bellow???

User-Agent: Googlebot
Allow: /

source:http://www.mattcutts.com/blog/new-robotstxt-tool

and using .htaccess we are currently using to disaalow badbot

RewriteCond %{HTTP_USER_AGENT} ^mister\ pix [NC,OR]
RewriteCond %{HTTP_USER_AGENT} ^Reaper [OR]
RewriteCond %{HTTP_USER_AGENT} ^Recorder [OR]
RewriteCond %{HTTP_REFERER} ^http://www.iaea.org$
RewriteRule !^http://[^/.]\.golpo.net.* - [F,L]

<Files php.ini>
Order allow,deny
Deny from all
</Files>

here what the mean of NC & FL ?

-- in other palce i read

SetEnvIfNoCase User-Agent "^EmailSiphon" bad_bot
SetEnvIfNoCase User-Agent "^EmailWolf" bad_bot
SetEnvIfNoCase User-Agent "^ExtractorPro" bad_bot
SetEnvIfNoCase User-Agent "^CherryPicker" bad_bot
SetEnvIfNoCase User-Agent "^NICErsPRO" bad_bot
SetEnvIfNoCase User-Agent "^Teleport" bad_bot
SetEnvIfNoCase User-Agent "^EmailCollector" bad_bot

<Limit GET POST>
Order Allow,Deny
Allow from all
Deny from env=bad_bot
</Limit>

---
we are really confused...any one can give us some tips...what is what ?
and is perfect?
which .htaccess is good to disallow badbots?