P2P Safety Checking
Download TorGuard's “Check My Torrent IP” tool and monitor your torrent client IP address. Because no one other than you has this torrent and there are no seeders, the torrent will not download or complete. Keep it active in your queue as long as you wish to view your torrent client's IP address. The Check my Torrent IP tool shows your torrent IP within your torrent client so you can constantly monitor your setup and the IP you show. Monitoring your torrent IP address will help you patch holes in your security practices in order to better safeguard your privacy. https://torguard.net/checkmytorrentipaddress.php
Open Port Check Tool
This is a free utility for remotely verifying if a port is open or closed. It is useful to users who wish to verify port forwarding and check to see if a server is running or a firewall or ISP is blocking certain ports. https://canyouseeme.org
DNS leak test
What is a DNS leak and why should I care?
When using an anonymity or privacy service, it is extremely important that all traffic originating from your computer is routed through the anonymity network. If any traffic leaks outside of the secure connection to the network, any adversary monitoring your traffic will be able to log your activity. https://dnsleaktest.com/
This service shows information about you.
This is the kind of information that all the sites you visit, as well as their advertisers and any embedded widget, can see and collect. https://ipleak.net/
Large number of Android VPN apps insecure https://www.ghacks.net/2017/01/31/large-number-of-android-vpn-apps-insecure
case study: https://research.csiro.au/ng/wp-content/uploads/sites/106/2016/08/paper-1.pdf
There are dozens of free and trial vpns on google play for mobile and they should be better inspected and checked before releasing on google play. Some of them just route a dns and not even encrypted. of course you can check on ipleaks or browserleaks but you should always pay attention to the permissions as well. I would agree and say to get a paid vpn also even if it's just for mobile. If you need a free one then do your homework first and make sure it is preferably outside the usa or not within the 5 eye countries.
No difference in once paid for vs. ones that are modded/hacked/patched/cracked. Only thing that one would be suspect about those types is them getting booted offline for some reason due to being modded/hacked/patched/cracked.