What you are asking is how to circumvent network policy and design.
(this is most likely a violation of the terms of service for your ISP.)
And usually for good reason, if your ISP is using wireless distribution, or any other back-haul that is HALF-Duplex, P2P will wreak havoc on it.
There are a number of reasons the ISP would block these services. You may disrupt the network service of everyone else trying to use the portion of the collision domain you are connected to. They may also be offering VOIP service over the same back-haul, which you could be on the hook for disrupting emergency call services.
They may just not want to deal with the legal concerns of copyright infringement for IP addresses that are assigned to them.
The old saying "you get what you pay for." seems like it fits here. If you want internet service that is unadulterated, PAY FOR IT.
"my concern is, whether I could use these domains to access other websites, or download using the unrestricted domains"
i read this as a general lack of concern for anyone else using the network service.
With all that being said, it is possible to do what you are trying to do.
but from a professional standpoint (and formerly administering a similar style policy). I couldn't, and will not give you advice on how to do so.
well, my ISP has allowed free connectivity over facebook and youtube. my concern is, whether I could use these domains to access other websites, or download using the unrestricted domains – Imesh Chandrasiri – 2018-02-13T19:59:38.787