apache config, htaccess for mixed http, https

Hi,
I am currently trying to setup following.
Following two are separate WordPress 4.5.3 installations–
a) https://example.com -> on https
b) https://site1.example.com -> on http

I am trying to make https://example.com to be multisite
and run network site https://multisite1.example.com and https://multisite2.example.com (networks sites to be http)

Note: There is ssl in the root installation. Not looking forward to make subdomains https..

Requirement: On one linux server/ IP address.
2 Separate wordpress installations, and one of them multisite.
Only root domain installation https and subdomains http installation and second subdomain install http as well.
I am facing problem in configuring it.
Problem: Multisite network site https://multisite1.example.com is redirecting to https://example.com
I doubt the issue is somewhere within htaccess rule. but not able to point that out.
Looking forward for a guidance on where I am doing wrong.

Following is the current apache config ->
a) for https://example.com

<VirtualHost *:80>
  ServerName www.example.com
  ServerAdmin [email protected]

Redirect 301 / https://example.com/
</VirtualHost>

<VirtualHost *:80>
 ServerName example.com
 ServerAlias multisite1.example.com multisite2.example.com
 ServerAdmin [email protected]
 DocumentRoot /var/www/html/example.com/docroot

  <Directory /var/www/html/example.com/docroot>
    Options Indexes FollowSymLinks MultiViews
    AllowOverride All
    Order allow,deny
    allow from all
  </Directory>

  ErrorLog /var/log/httpd/example.error.log
  LogLevel warn
 CustomLog /var/log/httpd/example.access.log combined
</VirtualHost>

Virtual host for https://site1.example.com

<VirtualHost *:80>
  ServerName www.site1.example.com
  ServerAdmin [email protected]

Redirect 301 / https://site1.example.com/
</VirtualHost>
<VirtualHost *:80>
  ServerName site1.example.com
  ServerAdmin [email protected]
  DocumentRoot /var/www/html/site1.example.com/docroot
  <Directory /var/www/html/site1.example.com/docroot>
  Options Indexes FollowSymLinks MultiViews
    AllowOverride All
    Order allow,deny
    allow from all
  </Directory>

  ErrorLog /var/log/httpd/site1.example.error.log
  LogLevel warn
 CustomLog /var/log/httpd/site1.example.access.log combined
</VirtualHost>

Following is htaccess->

#Begin https#
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{SERVER_PORT} 80
RewriteRule ^(.*)$ https://example.com/$1 [R,L]
</IfModule>
#End https#
#multisite setup begin
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]

# add a trailing slash to /wp-admin
RewriteRule ^wp-admin$ wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^(wp-(content|admin|includes).*) $1 [L]
RewriteRule ^(.*\.php)$ $1 [L]
RewriteRule . index.php [L]
</IfModule>
# multisite setup end#

Options -Indexes
Header unset Pragma
FileETag None
Header unset ETag
# EXPIRES CACHING ##
<IfModule mod_expires.c>
ExpiresActive On
ExpiresByType image/jpg "access 1 year"
ExpiresByType image/jpeg "access 1 year"
ExpiresByType image/gif "access 1 year"
ExpiresByType image/png "access 1 year"
ExpiresByType text/css "access 1 month"
ExpiresByType text/html "access 1 month"
ExpiresByType application/pdf "access 1 month"
ExpiresByType text/x-javascript "access 1 month"
ExpiresByType application/x-shockwave-flash "access 1 month"
ExpiresByType image/x-icon "access 1 year"
ExpiresByType audio/mpeg3 "access 1 year"
ExpiresDefault "access 1 month"
</IfModule>
## EXPIRES CACHING ##
<FilesMatch "\\.(js|css|html|htm|php|xml)$">
SetOutputFilter DEFLATE
</FilesMatch>
<IfModule mod_headers.c>
  <FilesMatch ".(js|css|xml|gz)$">
    Header append Vary: Accept-Encoding
  </FilesMatch>
</IfModule>

Following are the wp-config.php constants ->

define('FORCE_SSL_ADMIN', true);
$_SERVER['SERVER_PORT'] = 443;
/* Multisite */
define( 'WP_ALLOW_MULTISITE', true );
define('MULTISITE', true);
define('SUBDOMAIN_INSTALL', true);
define('DOMAIN_CURRENT_SITE', 'example.com');
define('PATH_CURRENT_SITE', '/');
define('SITE_ID_CURRENT_SITE', 1);
define('BLOG_ID_CURRENT_SITE', 1);
define( 'SUNRISE', 'on' );