The difference between the three products can be seen here: Features Comparison.
YES, If you are changing to a new antivirus product, you will need to uninstall the previous
antivirus scanner first. After uninstalling, you must reboot your PC before installing the new
If you are simply upgrading the existing antivirus software to a newer version of the same product, there is no need to uninstall the older version first. However, if the new version is two or more versions newer than the old, then you will want to uninstall the old version before installing the new. Again, anytime you uninstall an existing anti-virus product. In case of SecuraShield Ultimate Internet Security, even if you uninstall the older version after 5 months and again install the newer version after rebooting the system, it will automatically take the balance months of subscription.
It is never a good idea to run two antivirus scanners simultaneously. SecuraShield never recommends that and also make sure that the Windows Defender is off else you might get a system speed related issues which are most likely due to co-existence of Windows Defender and any antivirus product.
There are two ways of doing it:
Download the Latest Setup file from our website www.securashield.co.in and install this on your system, that has an option of PERFORM SCAN AUTOMATICALLY or ASK ME FOR ACTION and that also has Action options like Repair Automatically or Prompt me for action.
In case the laptop is formatted or OS is changed and you have to release the key to install again. Please use the following link to surrender your key: http://license.securashield.co.in/index.php/site/releasekey