1) MODIFY the zp-core/index.php and recopy the original for the installSignature(); and change the Offset from 0 to 2 in the same file.
2) In the DB zenphoto_install should be '' (blank) as the first change here makes the Signature
3) If you are unable to login after Upgrade place the following code in zp-core/setup/setup-option-defaults.php near line 36

	add '$oldhash = getOption('extra_auth_hash_text');'
		and edit 'setOptionDefault('extra_auth_hash_text', NULL);'
	to 'setOptionDefault('extra_auth_hash_text', (empty($oldhash) ? NULL : $oldhash));'

4) In sql file Gallery Title and Description are serialized so the serialization is done in our install.php
5) Copy the favicon.ico, robots.txt and /zp-data/.htaccess from the manual and configure them
6) In zenphoto.cfg keep ($conf['CHMOD'] = 0755;) not 775 not 0777 (If it is there)
7) In sql for every install it keep zenphoto_captcha_key same so NO need to change
8) Choose MySQLi as database engine in manual installation.
9) Always check for languages.
10) We rename /themes/default folder(if exists) during upgrade because after upgrading to 1.4.6 we get deprecated error message on end user page.
11) We configure "zenphoto.cfg.bak.php" because installation creates it.
12) PHP REQUIREMENT LINK : https://www.zenphoto.org/news/installation-and-upgrading/#--requirements ( While installation they have mentioned that they have tested this script on PHP 7.4 and shall not support any queries below PHP 7.4 as the recommended version is PHP 8+)
13) We don't support languages that are outdated.(Check this in every update in admin panel under 'Options->General' and add support only for languages that are checked by default)
14) keep the $conf['site_upgrade_state'] to "open" in zenphoto.cfg.php file to keep the site on open mode. (Default is maintenance mode in manual installation)
15) We have not deleted the themes and plugins folders in prezip function of upgrade.php because if the users has made any customization they shall get deleted. Also The upgrader ask to delete the unwanted files while upgrading.