Windows Defender is the default antivirus tool to protect your PC from viruses, malware, ransomware, and other security threats.
There are many ways to pass an object to a fragment. Serializable class is often used.
When your app consists of many modules and each module contains several fragments, you will need to hide or show menu items depending on the showing fragments.
Maximum upload file size is determined by 2 settings in php.ini file. They are upload_max_filesize and post_max_size.