Guess what?
Hostinger answered promptly. They moved my paid account from the server # 45 to the server # 80, that has a version of sql much newer. So I retry installing 2.8.2+ and the error discussed so far has NOT appeared again. The SQL appears as being OK with following details:
"mysql database (10.0.15-MariaDB) required version is 5.5.31 while you are running version 10.0.15 OK"
Now, the following errors continue to occur:
1. php_extension intl must be installed and enabled to get the best results (Intl extension is used to improve internationalization support, such as locale aware sorting)
2. php_setting opcache.enable PHP setting should be changed (PHP opcode caching improves performance and lowers memory requirements, OPcache extension is recommended and fully supported.)
I wonder if I'm the one who should set them correctly, or once again is Hostinger. Any help from your side is welcome and very much appreciated, as before either. Thank you.