Codeigniter 3 pagination with htaccess not working – SEO

I am trying to implement pagination in Codeigniter 3 but it always gives a 404 page not found error. I am using htaccess file to hide index.php.

My controller function is

$config = array();
$config['base_url'] = base_url('gallery');
$total_row = $this->gallery_model->record_count();
$config["total_rows"] = $total_row;
$config["per_page"] = 5;
$config['use_page_numbers'] = TRUE;
$config['num_links'] = $total_row;
$config['uri_segment'] = '4';
$config['cur_tag_open'] = '&nbsp;<a class="current">';
$config['cur_tag_close'] = '</a>';
$config['next_link'] = 'Next';
$config['prev_link'] = 'Previous';

$this->pagination->initialize($config); 

if($this->uri->segment(2))
{
    $page = ($this->uri->segment(2)) ;
}
else
{
    $page = 1;
}
$data["results"] = $this->gallery_model->fetch_data($config["per_page"], $page);

HTACCESS is as follows

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /lifeschool-genius/

### Canonicalize codeigniter URLs

# If your default controller is something other than
# "welcome" you should probably change this
RewriteRule ^(welcome(/index)?|index(.php)?)/?$ / [L,R=301]
RewriteRule ^(.*)/index/?$ $1 [L,R=301]

# Removes trailing slashes (prevents SEO duplicate content issues)
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.+)/$ $1 [L,R=301]

# Enforce www
# If you have subdomains, you can add them to 
# the list using the "|" (OR) regex operator
# RewriteCond %{HTTP_HOST} !^(www|subdomain) [NC]
# RewriteRule ^(.*)$ http://www.domain.tld/$1 [L,R=301]

# Enforce NO www
# RewriteCond %{HTTP_HOST} ^www [NC]
# RewriteRule ^(.*)$ http://domain.tld/$1 [L,R=301]

###

# Removes access to the system folder by users.
# Additionally this will allow you to create a System.php controller,
# previously this would not have been possible.
# 'system' can be replaced if you have renamed your system folder.
RewriteCond %{REQUEST_URI} ^system.*
RewriteRule ^(.*)$ /index.php/$1 [L]

# Checks to see if the user is attempting to access a valid file,
# such as an image or css document, if this isn't true it sends the
# request to index.php
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php?/$1 [L]
</IfModule>

<IfModule !mod_rewrite.c>
 # Without mod_rewrite, route 404's to the front controller
 ErrorDocument 404 /index.php
 </IfModule>

My Routes file is

$route['(:any)'] = "welcome/$1";
$route['default_controller'] = 'welcome';
$route['404_override'] = '';
$route['translate_uri_dashes'] = FALSE;

I had used the same code before in another project with Codeigniter 2 and it use to work fine. Please let me know what is wrong with this

Any help would be highly appreciated.

Thanks